
T HE VISCERA IN POSITION. 






TREATISE 



Physiology and Hygiene 



Educational Institutions and General 
Readers. 






FULLY ILLUSTRATED. 



BY 

JOSEPH C; HUTCHISON, M. D., 

President of the New York Pathological Society, Vice-President of the New York 

Academy of Medicine, Surgeon to the Brooklyn City Hospital, late President 

of the Medical Society of the State of New York, etc. 



NEW YORK: 

CLARK & MAYNARD, PUBLISHERS, 

5 BARCLAY STREET. 

1870. 



SCHOOL HISTORIES 

BY 

JOHN J. ANDEKSON, A. M. 



1. Introductory School History of the United 

States. Illustrated with maps. 195 pp. 16mo. 

This work, though arranged on the catechetical plan, may be read as a continuous 
narrative, the text having been fully written before the questions were prepared. 
It is designed tor classes of advanced as well as lower grades, in which 
only a very brief outline of the history of the country from its dis- 
covery to the present time is taught. 

2. Common School History of the United States. 

Illustrated with maps. 350 pp. 16mo. 

This work is more catechetical than the preceding, since the answers are more 
independent of each other. Designed for large graded schools. 

3. Grammar School History of the United States. 

With one series of maps showing the location of the places referred to; and another, 
showing the progress of the country in its territorial acquisitions and political 
divisions. 252 pp. 16mo. 

This work is on the narrative plan, with a set of questions for topical review at 
the end of the sections. It wtll meet all the wants of graded schools and 

ACADEMIES. 

4. Pictorial School History of the United States. 

Fully illustrated with maps, portraits, vignettes, &c 404 pp. 12mo. 

This work is also on the narrative plan, but more circumstantial in its statements 
than the preceding. Designed for high-schools and academies. 

*** Each of the above-named works contains the Declaration of Independence, 
and the Constitution of the United States, with questions and explanations ; and, in 
the Grammar School History, will also be found Washington's Farewell Address. 

5. A Manual of General History. 419 pp. i2mo. illus- 
trated with maps, showing the changes in the political divisions of the world, and 
giving the location of important places. Various tables of chronology and contem- 
poraneous events are also given, with a complete pronouncing index. Designed 

POR CLASSES OF ADVANCED GRADE. 

6. A School History of England. 300 pp. i2mo. illus- 
trated with maps, showing the geographical changes in the country at different 
periods. Chronological and genealogical tables are given ; also a complete pro- 
nouncing index. Designed for classes of advanced grade. 

7. Anderson's Bloss's Ancient History, illustrated with 

colored maps and a chart. 445 pp. 12mo. Designed for classes of high grade. 

]£P™ One of the leading aims in all of Anderson's Histories is to connect the geogra- 
phy with the chronology. 

CLARK & MAYNARD, Publishers, 

NEW YOEK. 



TO MY WIFE, 



"WHOSE SYMPATHY HAS, FOR MORE THAN TWENTY YEARS, LIGHTENED THIS 
CARES INCIDENT TO 



AN ACTIVE PROFESSIONAL LIFE, 



THIS HUMBLE VOLUME 



IS AFFECTIONATELY INSCRIBED. 



PREFACE. 



This work is designed to present the leading facts and principles 
of human Physiology and Hygiene in clear and concise language, 
so that pupils in schools and colleges, and readers not familiar with 
the subjects, may readily comprehend them. Anatomy, or a de- 
scription of the structure of an organ, is of course necessary to the 
understanding of its Physiology, or its uses. Enough of the former 
study has, therefore, been introduced, to enable the pupil to enter 
intelligently upon the latter. 

Familiar language, as far as practicable, has been employed, 
rather than that of a technical character. With a view, however, 
to supply what might seem to some a deficiency in this regard, a 
Pronouncing Glossary has been added, which will enable the in- 
quirer to understand the meaning of many scientific terms not 
in common use. 

In the preparation of the work the writer has carefully examined 
all the best material at his command, and freely used it ; the special 
object being to have it abreast of the present knowledge on the sub- 
jects treated, as far as such is possible in a work so elementary as 
this. The discussion of disputed points has been avoided, it being 
manifestly inappropriate in a work of this kind. 

Instruction in the rudiments of Physiology in schools does not 
necessitate the general practice of dissections, or of experiments upon 
animals. The most important subjects may be illustrated by draw- 



PREFACE. 4 

ings, such as are contained in this work. Models, especially those 
constructed by Auzoux of Paris, dried preparations of the human 
body, and of the organs of the lower animals, may also be used with 



The writer desires to acknowledge his indebtedness to R. M 
Wyckopf, M.D., for valuable aid in the preparation of the manu- 
script for the press; and to R Cresson Stiles, M.D., a skilful 
microscopist and physician, for the chapter " On the Use of the 
Microscope in the Study of Physiology." Mr. Avon C. Burnham, 
the well-known teacher of gymnastics, furnished the drawing of 
the parlor gymnasium and the directions for its use. 

Btvoklyn, N. Y., 1870. 



CONTENTS. 



CHAPTER I. 

PAGE 

THE FRAMEWORK OF THE BODY 15 

The Bones — Their form and composition — The Properties of Bone — The 
Skeleton — The Joints — The Spinal Column — The Growth of Bone — 
The Repair of Bone. 

CHAPTER II. 

THE MUSCLES 26 

The Muscles — Flexion and Extension — The Tendons — Contraction — 
Physical Strength — Necessity for Exercise — Its Effects — Forms of 
Exercise — Walking — Riding — Gymnastics — Open-air Exercise — 



CHAPTER III. 
THE INTEGUMENT, OR SKIN. 



The Integument — Its Structure — TJie Nails and Hair — The Complexion 
— The Sebaceous Glands — The Perspiratory Glands — Perspiration 
and its uses — Importance of Bathing — Different kinds of Batlis — 
Manner of Bathing — The Benefits of the Sun — Importance of 
Warm Clothing — Poisonous Cosmetics. 

CHAPTER IV. 

THE CHEMISTRY OF FOOD 53 

The Source of Food — Inorganic Substances — Water — Salt — Lime — Iron 
— Organic Substances — Albumen, Fibrin, and Casein — The Fats or 
Oils — The Sugars, Starch, and Gum — Stimulating Substances — 
Necessity of a Regulated Diet. 



CONTENTS. 



CHAPTER V. 

PAGE 
FOOD AND DRINK 64 

Necessity for Food — Waste and Repair — Hunger and Thirst — Amount 
of Food — Renovation of the Body — Mixed Diet — Milk — Eggs — Meat 
— Cooking — Vegetable Food — Bread — The Potato — Fruits — Purity 
of Water — Action of Water upon Lead — Coffee, Tea, and Chocolate 
—Effects of Alcohol. 

CHAPTER VI. 

DIGESTION 80 

The Principal Processes of Nutrition — The General Plan of Digestion — 
Mastication — The Teeth — Preservation of the Teeth — Insalivation 
— The Stomach and the Gastric Juice — The Movements of the 
Stomach — Gasti*ic Digestion — The Intestines — The Bile and Pan- 
creatic Juice — Intestinal Digestion — Absorption by means of Blood- 
vessels and Lacteals — The Lymphatic or Absorbent System — The 
Lymph — Conditions which affect Digestion — The Quality, Quan- 
tity, and Temperature of the Food — The Influence of Exercise and 
Sleep. 

CHAPTER VII. 

THE CIRCULATION 101 

The Blood — Its Plasma and Corpuscles — Coagulation of tJie Blood — The 
Uses of the Blood — Transfusioji — Change of Color — The Organs of 
ilie Circulation — Tlie Heart, Artei^ies, and Veins — The Cavities 
and Valves of the Heart — Its Vital Energy — Passage of the Blood 
through the Heart — Ihe Frequency and Activity of its Movements — 
The Pulse — The Spygmograph — T/te Capillary Blood-vessels — The 
Rate of the Circulation — Assimilation — InjuHes to the Blood-vessels. 

CHAPTER VIII. 

RESPIRATION 123 

The Objects of Respiration — TJie Lungs — The Air-Passages — Ihe Move- 
ments of Respiration — Expiration and Inspiration — TJieFrequency 
of Respiration — Capacity of the Lungs — The Air we Breathe — 
Changes in the Air from Respiration — Changes in the Blood — In- 
terchange of Gases in the Lungs — Comparison between Arterial and 



CONTENTS. 7 

Venous Blood — Respiratory Labor — Impurities of the Air — Dust — 
Carbonic Acid — Effects of Impure Air — Nature's Provision for 
Purifying the Air — Ventilation — Animal Heat. 

CHAPTER IX. 

PAGE 

THE NERVOUS SYSTEM 148 

Animal and Vegetative Functions — Sensation, Motion, and Volition — 
The Structure of the Nervous System — The White and Gray Sub- 
stances — Tlie Brain — Its Convolutions — The Cerebellum — The Spi- 
nal Cord and its System of Nerves — The Anterior and Posterior 
Roots — The Sympathetic System of Nerves — The Properties of Nerv- 
ous Tissue — Excitability of Nervous Tissues — The Functions of the 
Spinal Nerves and Cord — The Direction of the Fibres of the Cord — 
Reflex Activity and its Uses — The Functions of the Medulla Oblon- 
gata and the Cranial Ganglia — The Reflex Action of the Brain. 

CHAPTER X. 

THE SPECIAL SENSES 1*77 

The Production of Sensations — Variety of Sensations — General Sensi- 
bility — Pain and its Function — Special Sensation, Touch, Taste, 
Smell, Sight, and Hearing — The Hand, the Organ of Touch — The 
Sense of Touch — Delicacy of Touch — Sensation of Temperature and 
Weight — The Tongue the Organ of Taste — The Nerves of Taste — 
The Sense of Taste, and Us Relations with the other Senses — The 
Influence of Education on the Taste — Tlie Nasal Cavities, or the 
Organs of Smell — The Olfactory Nerve — The Uses of the Sense of 
Smell — The Sense of Hearing and Sound — The Ear, or the Organ 
of Hearing — The External, Middle, and Internal Ear — The Sense 
of Sight — Lights- Tlie Optic Nerve — The Eyeball audits Coverings — 
Ihe Function of the Iris — The Sclerotic, Choroid, and Retina — The 
Tears and their Function — Tlie Movements of the Eyeball — The 
Function of Accommodation. 

CHAPTER XI. 

THE VOICE 227 

Voice and Speech — Hie Larynx, or the Organ of the Voice — The Vocal 
Cords — The Laryngoscope — The Production of the Voice — The Use 
of the Tongue — The different Vai-ieties of Voice — The Change of 
Voice — Its Compass — Purity of Tone — Ventriloquy. 



8 CONTENTS. 

CHAPTER Xn. 

PAGE 

THE USE OP THE MICROSCOPE IX THE STUDY OF 

PHYSIOLOGY 236 

The Law of Tissues — Necessity of the Microscope — Different ki?ids of 
Microscopes — Additional Apparatus — Preliminary Studies — The 
Study of Human Tissues — Tissues of the Inferior Animals — Incen- 
tives to Study. 

APPENDIX. 

POISONS AND THEIR ANTIDOTES 247 

GLOSSARY 252 



LIST OF ILLUSTRATIONS. 



r». FAOB 

Frontispiece, ) m 

Viscera in Position, > 
i. Section of bone, 17 

2. Structure of bone, magnified, . . . . 17 

3. The skeleton, . . . . . . . .18 

4. Cells of cartilage, ....... 20 

5. Elbow-joint, . . . . . . . .21 

6. Spinal column, ........ 22 

7. The muscles, ........ 24 

8. Muscular tissue, magnified, ..... 25 

9. Biceps muscle of the arm, .... .26 

10. View of knee-joint, ....... 27 

11. Appliance for strengthening the muscles, . . . 35 

12. Appliance for strengthening the muscles, 35 
.13. Parlor gymnasium, ....... 36 

14. Root and transverse section of hair, magnified, . . 43 

15. Granules of potato starch, . . . . . .61 

16. Section of the trunk, . . . . . . . 81 

17. Section of a tooth, ....... 82 

18. Section of the jaws, 82 

19. Section of the jaws — right side, . . . . .84 

20. Structure of a salivary gland, 87 

21. Head of a horse, showing salivary gland, etc. . . 87 

22. Section of chest and abdomen, ..... 90 

23. Organs of digestion, 91 

24. The lacteals, 97 

25. Blood corpuscles, . . . . . . . .102 

26. Blood corpuscles of man and lower animals, . . 103 

27. Circulation of the blood. 108 



10 



LIST OF ILLUSTKATIO^S. 



28. Heart and large vessels, . 

29. Section of the heart, 

30. Form of the pulse, .... 

31. Valves of the veins, 

32. Web of frog's foot, magnified, . 

33. Circulation in a frog's foot, 

34. Organs of the chest, 

35. Larynx, trachea, and bronchial tubes, 

36. Diagram of the structure of the air-cells. 

37. Section of the lungs, 

38. Section of mouth and throat, . 

39. Ciliated cells, .... 

40. Cerebro-spinal system, 

41. Upper surface of the cerebrum, 

42. Vertical section of the brain, 

43. Base of the brain, .... 

44. Brain and spinal cord, 

45. Sense of touch, .... 

46. Section of nasal cavity, 

47. Front view of the eye, . 

48. Vertical section of eye, 

49. Diagram for blind point of eye, 

50. Retinal image, .... 

51. Different shapes of the globe of the eye, 

52. Function of accommodation, . 

53. Diagram of the ear, 

54. Section of the ear, .... 

55. Section of larynx and trachea, 

56. View of vocal cords by the laryngoscope, 

57. Different positions of vocal cords, . 

58. Simple microscope, .... 

59. Compound microscope, . 

60. Household microscope, 

61. Popular microscope., 



INTRODUCTION. 



' The Human Body is the abode of an immortal spirit, 
and is the most complete and perfect specimen of the 
Creator's handiwork. To examine its structure, to ascer- 
tain the uses and modes of action of its various parts, 
how to protect it from injury, and maintain it in a 
healthy condition, is the design of this work. 

The departments of knowledge which are concerned 
in these investigations, are the science of Human Physi- 
ology and the art of Hygiene. 

Physiology treats of the vital actions and uses of the 
various parts of living bodies, whether vegetable or ani- 
mal. Every living thing, therefore, has a Physiology. 
We have a Vegetable Physiology, which relates to plants ; 
and an Animal Physiology, relating to the animal king- 
dom. The latter is also divided into Comparative Physiol- 
ogy, which treats of the inferior races of animals, and 
Human Physiology, which teaches the uses of the various 
parts of the human body. 

Hygiene, or the art of preserving health, is the practi- 
cal use of Physiology. It teaches us how to cultivate our 
bodily and mental powers, so as to increase our strength 
and to fit us for a higher enjoyment of life. It also shows 
us how to prevent some of the accidents which may befall 
the body, and to avoid disease. It is proper that we should 



12 INTRODUCTION. 

understand the construction and powers of our bodies ; but 
it is our duty, as rational beings, to know the laws by which 
health and strength may be maintained and disease warded 
off. 

There are various means by which we gain important 
information respecting the Physiology of man. Plants 
aid us in understanding the minute structure of the hu- 
man body, its circulation, and absorption. From inferior 
animals we learn much in respect to the workings of the 
different organs, as we call those parts of the system which 
have a particular duty to perform. In one of them, as in 
the foot of the frog, we can study the circulation of the 
blood; in another, we can study the action of the brain. 

By vivisection, or the laying bare of some organ of a 
living animal, we are able to investigate certain vital 
processes which are too deeply hidden in the human body 
to be studied directly. This is not necessarily a cruel 
procedure, as we can, by the use of anaesthetics, so blunt 
the sensibility of the animal under operation, that he 
need not suffer while the experiment is being performed. 
There are other means by which we gather our informa- 
tion. There are occasionally men, who, from some acci- 
dent, present certain parts, naturally out of view, in 
exposed positions. In these cases, our knowledge is of 
much greater value than when obtained from creatures 
lower in the scale of being than man. 

"We are greatly aided, also, by the use of various instru- 
ments of modern invention. Chief among these is the 
microscope, which is, as we shall learn hereafter, an ar- 
rangement and combination of lenses in such a way as 
greatly to magnify the objects we wish to examine. 



INTRODUCTION". 13 



We haye much to say of Life, or vital activity, in the 
course of our study of Physiology ; but the most that we 
know of it is seen in its results. What Life is, or where its 
precise position is, we are not able to determine. We dis- 
cover one thing, however, that all the parts of the body 
are united together with wonderful sympathy, so that one 
part cannot be injured and other parts not suffer damage. 
It is further evident that all organs are not equally im- 
portant in carrying on the work of Life; for some may 
temporarily suspend their action, without serious results 
to the system, while others must never cease from acting. 
Yet there is nothing superfluous or without aim in our 
frames, and no part or organ can suffer harm without 
actual loss to the general bodily health. On this point 
Science and Holy Writ strictly agree. 



PHYSIOLOGY, 

AND 

HYGIENE. 



chapter i. 

The Framework of the Bodt. 

The Bones — Their Form and Composition — The Properties of Bone— 
The Skeleton — TJie Joints — The Spinal Column — The Growth of 
Bone — The Repair of Bone. 

1. The Bones. — The framework which sustains the 
human body is composed of the Bones. The superstructure 
consists of the various organs on which the processes of 
life depend. These organs are soft and delicately formed, 
and, if unprotected, would, in most cases, rapidly be de- 
stroyed when subjected to violence, however slight. The 
bones, having great strength and power of resistance, afford 
the protection required. 

2. The more delicate the organ, the more completely does 
Nature shield it. For example : the brain, which is soft in 
structure, is enclosed on all sides by a complete box of bone ; 
the eye, though it must be near the surface of the body 
to command an extensive view, is sheltered from injury 
within a deep recess of bone; the lungs, requiring freedom 
of motion as well as protection, are surrounded by a large 
case of bone and muscle. The bones serve other useful 
purposes. They give permanence of form to the body, by 

1 . The framework of the hody ? The superstructure ? Softness and delicacy 
of the organs ? How protected ? 

2. The more delicate the organ ? Example in relation to the brain ? The eye ? 
The lungs ? The services performed by the bones ? 



16 THE FRAMEWORK OF THE BODY. 

holding the softer parts in their proper places. They 
assist in movement, by affording points of attachment to 
those organs which have power of motion — the muscles. 

3. The Form and Composition of the Bones.— 

Their shape and size vary greatly in different parts of the 
body, but generally they are arranged in pairs, one bone for 
each side of the body. They are composed of both mineral 
and animal substances, united in the proportion of two 
parts of the former to one of the latter ; and we may sep- 
arate each of these substances from the other for examina- 
tion. First, if we expose a bone to the action of fire, 
the animal substance is driven off, or "burned out." "We 
now find that, though the shape of the bone is perfectly 
retained, what is left is no longer tough, and does not sus- 
tain weight as before. Again, we may remove the mineral 
portion, which is a form of lime, by placing a bone into a 
dilute acid. The lime will be dissolved out, and the shape 
of the bone remain as before; but now its firmness has 
disappeared, and it may be bent without breaking. 

4. If, for any reason, either of these ingredients is dis- 
proportionate in the bone during life, the body is in 
danger. The lime is useful in giving rigidity of form, 
while the animal substance insures toughness and elas- 
ticity. By their union, we are able to withstand greater 
shocks and heavier falls than would be possible with 
either alone. In youth, the period of greatest activity, 
the animal constituent is in excess: a bone then does 
not break so readily, but, when broken, unites with great 
rapidity and strength. On the other hand, the bones of 
old persons are more easily broken, and in some cases fail 
to unite. The mineral matter being then in excess, indi- 
cates that the period of active exertion is drawing to a 
close. 



4. Effect of deficiency of ingredient ? Usefulness of the lime ? Of the animal 
substance ? Effect of their union ? Condition, in youth ? Old age ? 



THE FRAMEWORK OF THE BODY. 



17 



5. The Structure of the Bones. — If we examine one 
of the long bones, which has been sawn through length- 
wise, we observe that it is admirably fashioned for affording 




Fig. 1.— Section of Bone. 

lightness as well as strength (Fig. 1). Its exterior is hard 
and resisting, but it is porous at the broad extremities, 
while through the central portion 
there is a cavity or canal which con- 
tains an oily material, called marrow. 
Let us now take a thin section of 
bone, and examine it under the mi- 
croscope; we discover that it is pierced 
by numerous fine tubes (Fig. 2), 
about which layers of bone-substance 
are arranged. Accordingly, though a 
bone be as hard as stone externally, it 
is by no means as heavy as stone, by 
reason of its light interior texture. 
Another element of power is found in 
the curved outline of the bones. The 
curved line is said to be " the line of 
beauty," as it certainly is the line of a S-The same more highly 
strength, and is uniformly employed ma s nified - 
in the bones whose position exposes them to accident. 




m 



Fig. 2. 
A.— Structure of bone en- 



5. In what respect admirably fashioned ? Its formation? Microscopic exam- 
ination ? The inference ? " Line of beauty ?" 



18 



THE FRAMEWORK OF THE BODY. 




Fig. 3.— The Skeleton. 



THE FRAMEWORK OF THE BODY. 19 

6. The Skeleton. — The number of bones in the human 
body exceeds two hundred. When these are joined together 
in the proper places, they form what is termed the Skeleton 
(Fig. 3). It embraces three important cavities. The first, 
surmounting the frame, is a box of bone, called the skull; 
below this, is a bony case, or "chest;" and lower down is 
a bony basin, called the pelvis. The two latter compose 
the trunk. The trunk and skull are maintained in their 
proper relations by the " spinal column." Branching from 
the trunk are two sets of limbs: the arms, which are 
attached to the chest by means of the " collar-bone" and 
"shoulder-blade;" and the legs, directly joined to the lower 
part of the trunk. 

7. The cavities of which we have spoken, are designed 
for the lodgment and protection of the more delicate and 
perishable parts of the system. Thus, the skull, together 
with the bones of the face, shelters the brain and the 
organs of four senses — sight, hearing, smell, and taste. 
The chest contains the heart, lungs, and great blood-ves- 
sels, while the lower part of the trunk sustains the liver, 
stomach, and other organs 

8. The Joints. — The point of union of two or more 
bones forms a joint or articulation, the connection being 
made in various ways according to the kind and amount 
of motion desired. The movable joints are compacted 
together by certain strong fibrous bands, called ligaments. 
These ligaments are of a shining, silvery whiteness, and 
very unyielding; so much so, that when sudden violence 
is brought to bear in the vicinity of a joint, the bone to 
which a ligament is attached may be broken, while the 
ligament itself remains uninjured. When this connect- 
ing material of the joints is strained or lacerated by an ac- 



6. Number of bones? Skeleton? The skull ? Chest? The trunk? The trunk 
and skull, how maintained ? What of the arms ? Legs ? 

7. Design of the cavities ? Give the examples. 

8. Joint or articulation ? Movable joints, how compacted? The ligaments of 
the movable joints ? What is a sprain ? Consequence of a serious sprain ? 



20 THE FRAMEWORK OF THE BODY. 

cident, a " sprain" is the consequence. An injury of this 
sort may be, and frequently is, quite as serious as the 
breaking of a bone. 

9. The ligament, then, secures firmness to the joint; 
it must also have flexibility and smoothness of motion. 
This is accomplished by a beautiful mechanism the perfec- 
tion of which is only feebly imitated by the most ingenious 
contrivance of man. The ends of the bones are covered 
by a thin layer of cartilage, which being smooth and elas- 
tic, renders all the movements of the joint very easy. In 
addition to this, there is an arrangement introduced for 
" lubricating" the joint, by means of a delicate sac con- 
taining fluid. This fluid is constantly supplied in small 
quantities, but only so fast as it is used up in exercise. 
In appearance, it is not unlike the white of an egg, and 
hence its name synovia, or egg-like. 

10. Thus, we observe, that two 
very different substances enter into 
the composition of a joint. The 
ligament, very unyielding, affords 
strength, while the cartilage, elastic 
and moist, gives ease and smooth- 
ness of motion. The amount of 
motion provided for varies greatly 
in different joints. In some there is 
none at all, as in the skull, where 
one bone is dove-tailed into another 
by what are termed sutures. Others 
have a hinge-like motion, such as 

Fig. 4,-Cells of Cartilage. ^ qsq Q f foe elbow, wrist, ankle, 

and knee ; the most complete of these being the elbow- 
joint (Fig. 5). Belonging to another class, the ball-and- 

9. Office of the ligament ? What must it have ? How accomplished ? Describe 
it Synovia ? 

1 0. What do we observe as resards the composition of a joint ? The ligament 
and cartilage ? What varies ? Example of the skull ? Other examples ? The 
ball-and-socket joint? 




THE FRAMEWORK OF THE BODY. 



21 



socket joint, is that at the shoulder, possessing a freedom 
of motion greater than any other in the body. 




Fig. 5.— Elbow Joint. A, Bone of the arm ; B, C, Bones of the fore-arm. 



11. The Spinal Column. — The spinal column is often 
spoken of as the " back-bone," as if it were a single bone, 
while, in reality, it is composed of a chain, of twenty-six 
small bones, called vertebra. The spinal column is a 
wonderful piece of mechanism. It not only connects the 
important cavities of the body, as has already been shown, 
but, also, itself forms a canal, which contains the spinal 
cord. The joints of the vertebrae are remarkable for the 
thick layers of cartilage which separate the adjacent sur- 
faces of bone. The amount of motion between any two 
of these bones is not great; but these little movements, 
taken together, admit of very considerable flexibility, in 
several directions, without endangering the supporting 
power of the column. 



22 THE FRAMEWORK OF THE BODY. 

12. The abundant supply of intervertebral cartilage lias 
another important use, namely, it adds greatly to the 
elasticity of the frame. It is due, in part, 
to this elastic material, and in part to the 
frequent curves of the spine, that the brain 
and other delicate organs are protected from 
the shock of sudden falls or jars. During 
the day, the constant pressure upon these 
joints, while the body is erect, diminishes 
the thickness of the cartilages; so that a 
person is not so tall in the evening as in 
the morning. The effects of this compres- 
sion pass away when the body reclines in a 
horizontal position. 

13. The Growth of Bone.— Bone, like 
all the other tissues of the body, is con- 
stantly undergoing change, old material 
being withdrawn, and new particles taking 
their place. This has been shown conclu- 
sively by experiments. If an animal be fed 
with madder — a red coloring matter — for a 
day or two, the bones soon become tinged ; 
then, if the madder be discontinued for a 
few days, the original color returns. If, how- 
ever, this material be alternately given and 
withheld, at short intervals, the bone will 
be marked by a succession of red and white 
rings. In very young animals, all the bones 
become colored in a single day; in older 
fig. 6.— the ones, a longer time is required. The process 

Spinal Column. „ . -. . ,. 1 , . x 

oi waste and repair, therefore, is constantly 
taking place in this hard substance, and with astonishing 
rapidity. 

12. Elasticity of the frame ? Protection of the brain from shocks TallneBS 
of persons ? Effects of reclining ? 

13. Change in bone? Example— animal and madder. Rapidity of change in 
color? Waste and repair? 



THE FRAMEWORK OF THE BODY. 23 

14. The Repair of Bone. — Nature's provision for 
uniting broken bones is very complete. At first, blood is 
poured out around the ends of the bone, as a result of 
the injury. This is gradually absorbed, and gives place 
to a watery fluid, which, thickening from day to day, ac- 
quires, at the end of two weeks, the consistency of jelly. 
This begins to harden, by a deposit of new bone-substance, 
until, at the expiration of five or six weeks, the broken 
bone may be said to be united. It is, however, still fragile, 
and must be used carefully a few weeks longer. The 
process of hardening continues, and months must pass 
before the union can be said to be complete. 



QUESTIONS FOR TOPICAL REVIEW. 

PAGE 

1. What useful purposes do the bones serve ? 15,16 

2. State what you can of the composition of the bones 16 

3. Of the usefulness of lime in the bones ... 16 

4. Of the usefulness of animal substance in the bones 16 

5. State what you can of the structure of the bones 17 

6. Of the strength belonging to the bones. 15. 16, 17 

7. What is meant by the human skeleton ? 1^ 

8. Give a description of its construction 19 

9. What is meant by a joint in the human frame ? 19 

10. State what you can of the movable joints 19, 20 

11. What office is performed by the ligaments of the joints ? 19, 20 

12. What by the cartilage at the joints ? 20 

13. What movable joints are there ? 20, 21 

14. Describe the construction of the spinal column 21 

15. What properties and powers does the spinal column possess ? 21, 22 

16. When is a person taller than at other times ?. 22 

17. Give the reason for this 22 

18. What can you state of the growth of bone? 22 

19. Describe the process by which a broken bone is repaired 28 



24 



THE MUSCLES. 




Fiq. 7.— The Muscles. 



THE MUSCLES. 



25 



chapter ii. 

The Muscles. 

The Muscles — Flexion and Extension — The Tendons — Contraction — 
Physical Strength— Necessity for Exercise— Its Effects— Forms of 
Exercise — Wa Iking — Biding — Gymnastics — Open-air Exercise — 
Sleep — Recreation. 

1. The Muscles. — The great mass of the body exter- 
nal to the skeleton, is composed of the flesh, or Muscles, 
which largely determines its outline and weight. The 
muscles are the organs of motion. Their number is 
about four hundred, and to each of them is assigned a 
separate and distinct office. They haye all been studied, 
one by one, and a name given to each, by the anatomist. 
Each is attached to bones which it is designed to move. 
A few are circular in form, and enclose cavities, the size 
of which they diminish by contraction. 

2. If we examine a piece of flesh, we observe that it is 
soft, and of a deep red color. Its structure appears to be 

composed of layers 
and bundles of small 
fibres. Let us fur- 
ther examine these 
fibres under the mi- 
croscope. We now 
discover that they 
are, in turn, made up 
of still finer fibres, 
or fibrillcB : these are 
seen in Fig. 8. The 
fibres are beautifully 




Fig. 8.— Muscular Tissue. 

a, £>, Striped muscular fibres : c, The same more 

highly magnified. 



1 . What are the muscles ? Their number ? The design of most of them ? Of 
a few ? 

2. The structure of flesh? Its color, etc.? The composition of the fibres? 
How marked ? 

2 



26 



THE MUSCLES. 



marked by parallel wavy lines, about ten thousand to an 
inch, which give the fibre its name of the striped muse alar 
fibre. All of the voluntary muscles present this appearance. 
-3. Flexion and Extension. — The muscles are, for 
the most part, so arranged in pairs, or corresponding 
sets, that when motion is produced in one direction by 
one set, there is, opposite to it, another 
muscle, or group of muscles, which 
b brings the limb back to its place. When 
they act alternately, a to-and-fro move- 
ment results. When a joint is bent, the 
motion is called flexion; and when it is 
made straight again, it is called exten- 
sion. When both sets act equally, and 
I the same moment, no motion is pro- 
duced, but the body or limb is main- 
tained in a fixed position: this occurs* 
when we stand erect. The muscles 
which produce extension are more pow- 
erful than those opposite to them. 

4. The muscles are also distinguished, 
on the other hand, as the voluntary 
and involuntary muscles, according as 
they are, or are not, under the control 
of the will. The heart is an example of 
the involuntary variety. We cannot 
change its action in the least by an 
effort of the will. When we sleep, and 
the will ceases to act, the heart contin- 
ues to beat without cessation. The voluntary muscles, 
on the other hand, are such as are used only when we wish 
or will to use them — as the muscles of the hand or arm 
(Fig. 9). 




Fig. 9.— A. Bicep 
cle of the arm: 
Its tendons. 



3. Arrangement of the muscles? Their action ? Flexion and extension ? Ac- 
tion of the muscle? when we stand erect ? 

4. Kinds of muscles? The voluntary? Involuntary? The heart? Give the 
example. The hand ? Arm ? 



THE MUSCLES. 



27 



5. The Tendons. — Tendons, or sinews, are the ex- 
tremities of muscles, and are compactly fastened upon 
bone. They are very strong, and of a silvery whiteness. 
They may be felt just beneath the skin, in certain parts of 
the body, when the muscles are being used, as at the bend 
of the elbow or knee. The largest tendon of the body is 
that which is inserted into the heel, called the tendon of 
Achilles, after the hero of the Grecian poet, the fable relat- 
ing that it was at this point that he received his death- 
wound, no other part of his body being vulnerable. The 
muscles which extend into the leg unite to form a single 




Fie. 10. -View of Knee-joint. A. Thigh hone: B, Knee-pan : C. D, Leg hones. 

and very powerful tendon, and enclose a small bone called 
the knee-pan, which, acting like a pulley, greatly increases 
their power, and at the same time protects the front of the 
knee-joint (Fig. 10). 

6. Muscular Contraction. — The muscles, when acted 
upon by the appropriate stimulus, contract, or so change 



5. What are the tendons or sinews? Their strength? Color? Location? 
Tendon of Achilles ? The fahle ? Muscles of the leg ? 

6. Contraction of the muscles ? Bending of the arm or finger ? Other agencies ? 
Automatic movements ? In cold-blooded animals ? 



28 THE MUSCLES. 



their shape, that their extremities are brought nearer to- 
gether. The bending of the arm, or of a finger, is effected 
in this manner, by the will; but the will is not the only 
means of producing this effect. Electricity, a sharp blow 
over a muscle, and other stimuli, also cause it. Contrac- 
tion does not always cease with life. In man, after death 
from cholera, automatic movements of hands and feet 
have been observed, lasting not less than an hour. In 
certain cold-blooded animals, as the turtle, contraction 
has been known to take place for several days after the 
head has been cut off. 

7. The property which, in muscle, enables these move- 
ments to take place is called contractility. If we grasp a 
muscle while in exercise (for example, the large muscle in 
the front of the arm), we notice the alternate swelling and 
decrease of the muscle, as we move the forearm to and fro. 
It was at one time supposed that the muscle actually in- 
creased in volume during contraction. This, however, is 
not the case; for the muscle, while gaining in thickness, 
loses in length in the same proportion; and thus, the 
volume remains the same in action and at rest. 

8. Contraction is not the permanent, or normal, state 
of a muscle. It cannot long remain contracted, but after 
a shorter or longer time, it wearies and is obliged to relax. 
After a short rest, it can then again contract. It is for 
this reason that the heart can beat all through life, night 
and day, by having, as we shall hereafter see, a brief inter- 
val of rest between successive pulsations. For the same 
reason, it is more fatiguing to stand for any great length of 
time in one position, than to be walking the same period. 

9. Relative Strength of Animals. — The amount 
of muscular power which different animals can exert, has 

7. Contractility? Give the illustration. What was supposed? What is the 
case ? 

8. What further in relation to contraction ? Weariness of a muscle ? Beating 
of the heart ? Standing and walking ? 

9. Muscular power of animals ? How tested? Man's power? Horse's? The 
comparison ? 



THE MUSCLES. 29 

been tested by experiment. By determining the number 
of pounds which an animal can drag upon a level surface, 
and afterward comparing that with its own weight, we can 
judge of its muscular force. It is found that man is able 
to drag a little less than his own weight. A draught-horse 
can exert a force equal to about two-thirds of his weight. 
The horse, therefore, though vastly heavier than man, is 
relatively not so powerful. 

10. Insects are remarkable for their power of carrying 
objects larger and heavier than themselves. Many of 
them can drag ten, and even twenty times their weight. 
Some of the beetles have been known to move bodies more 
than forty times their own weight. So far, therefore, from 
it being a fact that animals have strength in proportion 
to their weight and bulk, the reverse of that statement 
seems to be the law. 

11. Physical Strength. — The difference in strength, 
as seen in different individuals, is not due to any original 
difference in their muscles. Nature gives essentially the 
same kind and amount of muscles to each person, and the 
power of one, or the weakness of another, arises, in great 
part, from the manner in which these organs are used or 
disused. 

12. Many authors complain of the physical degeneracy 
of men at the present- day, as compared with past genera- 
tions. There is room -for "doubt as to the correctness of 
this statement. Certain experiments^! a ve recently been 
made with the metallic armor worn seven hundred years 
ago, by which it is found that any man, of ordinary height 
and muscular development, can carry the armor and wield 
the weapons of an age supposed to be greatly our superior 
in strength. When we consider that in those days, only 
very strong men could endure the hardships of soldier-life, 

10. Power of insects? Beetles? Give the conclusion. 

1 1 . Difference in strength of individuals ? How caused ? 

12. Complaint in relation to degeneracy? How true? How determined >»y 
armor ? The fair supposition ? 



30 THE MUSCLES. 



it is fair to suppose that our age has not so greatly degen- 
erated in respect to physical strength. 

13. Importance of Exercise. — Action is the law of 
the living body. Every organ demands use to preserve 
it in full vigor, and to obtain from it its best services. 
The value of that training of the mind, which we call 
education, is everywhere recognized. The child is early 
put to school, and for many years continues to study, in 
order that his brain, which is the great centre of mental 
power, may act healthfully and with force. It is impor- 
tant that the body, also, should receive its education by 
exercise. This is especially true of persons belonging to 
certain classes of society, whose occupation confines them 
within doors, and requires chiefly brain-work. 

14. Persons who are engaged in manual labor in the 
open air obtain all the exercise necessary for bodily health 
in their regular business: their need is more likely to be a 
discipline or exercise of the mind. A perfect business of 
life, therefore, would be one which would combine both 
physical and mental labor in their proper proportions. 
If such a business were possible for all the human race, life 
would thereby be vastly prolonged. Such is, in fact, to a 
large extent, the occupation pertaining to one period of 
life — childhood. A part of the time is spent by the child 
in improving his mind by study, and another part of the 
time he has physical exercise in his games and sports. 

15. The Effects of Exercise. — Exercise consists in 
a well-regulated use of the voluntary muscular system. 
The effects, however, are not limited to the parts used. 
Other organs, which are not under the control of the 
will, are indirectly influenced by it. For instance, the 
heart beats more rapidly, the skin acts more freely, and 



13. Action? Use of organs? Training of the mind? The child's brahi ? 
Education of the bodv ? 

14. Work in the open air ? A perfect business ? The consequence of universal 
perfect business ? Occupation of children ? 

1 5. In what does exercise consist ? Effects of it ? 



THE MUSCLES. 31 

becomes hotter, as well as the parts beneath it, and the ap- 
petite and power of digestion are increased. An increased 
exhalation from the lungs and skin purifies the current of 
the circulation, and the body as a whole thrives under its 
influence. 

16. The immediate effect of exercise, however, is upon 
the muscles themselves; for by use they become firm and 
large, and increase in power. If we examine a muscle thus 
improved by exercise, we find that its fibres have become 
larger and more closely blended together, that its color is 
of a darker red, and that the supply of blood-vessels has 
increased. Without exercise the muscle appears thin, 
flabby, and pale. On the other hand, excessive exercise, 
without sufficient relaxation, produces in the muscle a 
condition not very different from that which follows dis- 
use. The muscle is worn out faster than nature builds it 
up, and it becomes flabby, pale, and weak. 

17. Violent exercise is not beneficial ; and spasmodic 
efforts to increase the muscular strength are not calculated 
to secure such a result. Strength is the result of a gradual 
growth, and is most surely acquired if the exercise be 
carried to a point short of fatigue, and after an adequate 
interval of rest. To gain the most beneficial results, the 
exercise should be at regular hours, and during a regular 
period. The activity of the exercise, and the time de- 
voted to it must vary, of course, with the strength of the 
individual, and should be carefully measured by it. \ 

18. Different Modes o£ Exercise. — There are very 
few who have not the power to walk. There is required 
for it no expensive apparatus, nor does it demand a period 
of preliminary training. Walking may be called the uni- 
versal exercise. With certain foreign nations, the English 

16. General effect upon the muscles? Special effect? Effects of inaction? 
Of excessive exercise? 

17. Of violent and spasmodic efforts? Strength, how attained? Give the 
particulars. 

1 8 . What may walking he called ? What further is said of walking ? 



32 THE MUSCLES. 



especially, it is a very popular exercise, and is practised 
habitually by almost every class of society ; by the wealthy 
as well as by those who have no carriages; by women as 
well as by men. 

19. Eunning, leaping, and certain other more rapid and 
violent movements, are the forms of exercise that are 
most enjoyed in childhood. For the child, they are not 
too severe, but they may be so prolonged as to become 
injurious. Instances have been recorded where sudden 
death has resulted after violent playing, from overtaxing 
the heart: for example, we have the case of a young girl 
who, while skipping the rope, and endeavoring to excel 
her playmates by jumping the greatest number of times, 
fell dead from rupture of the heart. 

20. Carriage-riding, as a means of passive exercise, is par- 
ticularly well suited to invalids, and persons advanced in 
life. Horseback exercise brings into use a greater number 
of muscles than any other one exercise, and with it there 
Is an exhilaration of feeling which refreshes the mind at the 
same time. It is one of the manliest of exercises, but not 
less suitable for women than for men. To be skilful in 
riding, it is best to begin its practice in youth ; but there 
are very few kinds of exercise of which the same is not 
equally true. 

21. For those who live near streams or bodies of water, 
there are the delightful recreations of boating, swimming, 
and skating. Certain of these exercises have a practical 
importance aside from and above their use in increasing 
the physical vigor. This is especially true of boating and 
swimming, since they are often the means of saving life. 
Practice in these exercises also teaches self-reliance, 
courage, and presence of mind. Persons who have become 
proficient in these vigorous exercises are generally the ones, 

19. What is said of running, and other like movements? What, as related to 
childhood? What instances are alluded to ? Example? 

20. Carriage-riding? Horsehack-riding? 

21. Boating, swimming, and skating? 



THE MUSCLES. 33 



who, in times of danger, are the quickest to act and the 
most certain to do so with judgment. 

22. Physical Culture.— That form of exercise which 
interests and excites the mind, will yield the best results ; 
but to some persons no kind of exertion whatever is, at 
first, agreeable. They should, nevertheless, make a trial 
of some exercise, in the expectation that, as they be- 
come proficient in it, it will become more pleasant. In 
exercise, as many sets of muscles should be employed 
as possible, open-air exercise being the best. Parlor 
gymnastics, and the discipline of the gymnasium are 
desirable, but they should not be the sole reliance for 
physical culture. No in-door exercise, however excellent 
in itself, can fill the place of hearty and vigorous activity 
in the open air. 

23. Gymnastic Exercises for Schools and Col- 
leges. — In the system of education among the ancients, 
physical culture predominated. In ancient Greece, physi- 
cal exercises in schools were prescribed and regulated by 
law, and hence these schools were called gymnasia. At 
the present time, on the contrary, this culture is almost 
wholly unknown, as a part of the course of education, in 
our schools and colleges. In a few of our institutions of 
learning, however, physical exercises have been intro- 
duced, with manifest advantage to the students, and they 
form a part of the regular curriculum of exercises, — as 
much so as the recitations in geography, grammar, or 
Greek. The good effect of the experiments, as shown in 
improved scholarship as well as increased bodily vigor, in 
the institutions where the plan has been tried, will, it is 
hoped, lead to its universal adoption. We should then 
hear less frequently of parents being- obliged to withdraw 
their children from school, because they become exhausted 

22. What kind of exercise yields the best results ? What advice ie given ? 

23. Physical culture among the ancients ? In Greece ? In schools and colleges 
at the present time ? Result to the body and mind ? 



34 THE MUSCLES. 

or, perchance, have lost their health from intense and pro- 
tracted mental application. 

24. Were gymnastics more common in our educational 
institutions we should not so often witness the sad spectacle 
of young men and women leaving our colleges and semi- 
naries, with finished educations it may he, hut with consti- 
tutions so impaired, that the life which should be devoted 
to the accomplishment of noble purposes must be spent in 
search of health. Spinal curvatures, which, according to 
the experience of physicians, are now extremely frequent, 
especially among ladies, would give place to the steady 
gait and erect carriage which God designed his human 
creatures should maintain. 

25. All the exercises necessary for the proper develop- 
ment of the body may be obtained from the use of a few 
simple contrivances that every one can have at home, at 
little cost — less by far than is spent for useless toys. Many 
of these may be made available in the parlor or chamber, 
though all exercises are far more useful in the open air. A 
small portion of the day thus spent will afford agreeable 
recreation as well as useful exercise. The Indian club, the 
wand, the ring, and the dumb-bells answer ordinary pur- 
poses very well. Illustrations are here introduced of a few 
simple contrivances that may be useful for general exer- 
cises, and are specially suitable for persons with weak 
spines, or with spines that are the subject of lateral curva- 
ture. 

26. One of the simplest appliances for strengthening 
the muscles of the spine, designed chiefly to exercise the 
muscles on either side of the spine, consists of two wooden 
handles attached to india-rubber cords, one of which is 
attached to a hook made fast in the ceiling, or in the top 
of the door-case ; and the other to another hook fastened 
in the wall, door-post, or window-casing, about the height 

24. The result of gymnastics in our colleges and other institutions of learning? 



THE MUSCLES. 



35 



of the shoulder. When traction is made with the left hand, 
it exercises the muscles on the left side of the spine, while 




those on the opposite side are left almost at rest, owing to 
the oblique direction given to the shoulders when the right 




hand grasps the horizontal cord. (This appliance will he 
understood by referring to Fig. 13.) 



36 



THE MUSCLES. 



27. Fig. 11 shows an appliance consisting of two strong 
elastic cords, with handles, secured to a hook in the floor, 
so arranged that the patient has to stoop forward to reach 
them. On raising the body the spinal muscles are power- 
fully exercised. Fig. 12 shows other modes of using the 
elastic cords for strengthening the spine and chest. 





28. These various appliances have been combined so as 
to form a system of gymnastics suitable for parlor use ; 
other appliances have been added by which the muscles of 



THE MUSCLES. 37 

the legs may be called into action as well as those of the 
spine and upper part of the body (Fig. 13). Combinations 
of cords suitable for particular cases may also be made, and 
by using one or several cords on the same hook, their power 
may be adapted to the strength of the most robust as well 
as to that of the invalid, or of the most delicate child. 
The entire apparatus is quite simple in its construction 
and inexpensive, requiring but little space, and at the 
same time affording a great variety of exercises. 

EXEECISES THAT MAY BE PRACTISED ON THIS APPA- 
RATUS. 

Exercise I. (Fig. 13). — Stand erect under the cords and place the 
heels together. Grasp the handles firmly, keeping the knees and 
elbows stiff, and pull downward and forward until the fingers nearly 
touch the toes. Return slowly to the erect position. Repeat. 

Exercise II. (Fig. 13). — Stand erect, and having grasped the 
handles overhead firmly, separate them and bring them down 
slowly until they touch the sides : then return them slowly to the 
original position. Repeat. 

Exercise III. (Fig. 13). — Stand erect, heels together, grasp the 
handles overhead, and charge forward with the right foot. Return 
to first position, and then charge with the left. Repeat, using the 
right and left foot alternately. 

Exercise IV. (Fig. 13). — Stand erect, heels together. Grasp the 
handle overhead, and charge forward with the right foot, knee bent. 
Remain in this position and bring the arms down to the sides so that 
the arm and fore-arm may form a right angle. Still holding the 
handles, thrust forward, first the right hand and then the left, until 
the arm is straight. Repeat. Return to first position, then charge 
forward with the left foot, performing the same movements as before. 

Exercise Y. (Fig. 13). — In this exercise we change to the pulleys 
leading from the side posts, which can be used in several different 
ways. 1st. Stand erect, heels together, facing one of the posts, 
grasp the handle with the right hand, the arm being extended, then 
flex the fore-arm on the arm. Repeat. Perform the same move- 
ments with the left hand. 2d. Stand with back to the post ; grasp 
the pulley behind with the right hand, then gradually bring the 
hand forward until it is extended in a straight line in front. Repeat. 
Perform the same exercise with the left hand. 



38 THE MUSCLES. 



Exercise VI. (Fig. 13). — This exercise is especially adapted to the 
legs. StiiTups are so arranged that they can be attached to the 
pulleys overhead, and can hang down to within three or four feet of 
the floor. Place the foot in the stirrup, and then press down until it 
touches the floor. Repeat. Exercise the left foot in the same way. 

Exercise VII. (Fig. 13). — This exercise requires a little attention 
in the adjustment of the apparatus. Under the pulleys in the floor 
are passed ropes which can be attached to the snap-hooks that hold 
the handles overhead. Stoop forward with the knees stiff", and take 
hold of the handles, and then raise the body to the erect position. 
Repeat. 

Exercise VIII. (Fig. 13).— Sit on the floor or on a seat three or 
four inches high ; bend forward, take hold of the handles, and per- 
form the same movements that you would in rowing a boat. 

Exercise IX. (Fig. 13). — The trapeze can now be let down ; take 
hold of it with both hands, sustaining the weight of the body with 
the arms, then rotate the body first from right to left, then from left 
to right alternately. This exercise is especially suitable for females. 

Exercise X. (Fig. 13). — Grasp the trapeze as before, bearing all 
the weight with the arms : then draw the body up slowly until you 
can place the chin over the bars. This requires strength of muscle, 
and might strain if done too violently ; if slowly performed there is 
no danger. 

These are but a few of the exercises that can be practised with 
this apparatus. As these become familiar they can easily be modi- 
fied, and new ones can be arranged to meet the requirements of 
particular cases. Most of the exercises described can be practised 
with one hand so as to strengthen the muscles on one side. 

29. Rest. — We cannot always be active: repose must 
succeed labor. We obtain this rest partly by suspending 
all exertion, as in sleep, and partly by a change of employ- 
ment. It is said that Alfred the Great recommended that 
each day should, be divided in the following manner: 
"Eight hours for work, eight hours for recreation, and 
eight hours for sleep." This division of time is as good as 
any that could now be made, if it be borne in mind that, 
when the work is physical, the time of Tecreation should 



Alfred the Great ? The eight- 



THE MUSCLES. 39 

be devoted to the improvement of the mind; and -when 
mental, we should then recreate by means of physical 
exercise. _ __^-— 

30. During sleep, all voluntary activity ceases, the rapid- 
ity of the circulation and breathing diminishes, and the 
temperature of the body falls one or two degrees. In con- 
sequence, the body needs warmer coverings than during 
the hours of wakefulness. During sleep, the body seems 
wholly at rest, and the mind is also inactive, if we except 
those involuntary mental wanderings which we call dreams. 
Nevertheless a very active and important physical process 
is going on. Nutrition, or the nourishing of the tissues, 
now takes place. While the body is in action, the process 
of pulling down predominates, but in sleep, that of build- 
ing up takes place more actively. In this way we are re- 
freshed each night, and prepared for the work and pleasures 
of another day. If sleep is insufficient, the effects are seen 
in the lassitude and weakness which follow. Wakefulness 
is very frequently the forerunner of insanity, especially 
among those who perform excessive mental labor. 

31. All persons do not require the same amount of sleep, 
but the average of men need from seven to nine hours. 
There are well-authenticated cases where individuals have 
remained without sleep for many days without apparent 
injury. Frederick the Great required only five hours of 
sleep daily. Bonaparte could pass days with only a few 
hours of rest. But this long continued absence of sleep is 
attended with danger. After loss of sleep for a long period, 
in some instances, stupor has come on so profoundly, that 
there has been no awaking. 

32. There are instances related of sailors falling asleep 



30. Cessation of voluntary activity ? Temperature of the body ? Consequence ? 
Body and mind during sleep ? Nutrition ? Describe it. Consequence of insuffi- 
cient sleep ? 

31. Amount of sleep in different persons? Cases? Frederick the Great? 
Bonaparte ? Instances of long deprivation of 6leep ? 

32. Instances of sailors ? French soldiers ? During torture ? 



40 THE MUSCLES. 



on the gun-deck of their ships while in action. On the 
retreat from Moscow, the French soldiers would fall asleep 
on the march, and could only be aroused by the cry, " The 
Cossacks are coming !" Tortured persons are said to have 
slept upon the rack in the intervals of their torture. In 
early life, while engaged in a laborious country practice, 
the writer not unfrequently slept soundly on horseback. 
These instances, and others, show the imperative demand 
which nature makes for rest in sleep. 



QUESTIONS FOR TOPICAL REVIEW. 

PAGE 

1. What can you state of the number and division of the muscles ? 25, 26 

2. Describe the structure of the muscles 25, 26 

3. Their arrangement in pairs and consequent action 26 

4. What is the difference between the motion called flexion and that called 

extension ? 26 

5. Describe their action, and state which are the more powerful 23 

6. What is the difference between voluntary and involuntary muscles ? 26 

7. Illustrate the difference between the two 26 

8. State all you can of the tendons or sinews 2? 

9. What is meant by contraction of the muscles ? 27, 2S 

10. In how many and what ways may contraction be effected ? 2S 

11. What is stated of after-death contraction ? 28 

12. Why cannot a muscle in life continue contracted a long time ? 2S 

13. How then can the constant beaferhg ofHhe heart be explained ? 2S 

14. How does the strength of a man compare with that of a horse ? 29 

15. What can you state in relation to the relative strength of animals ? 28, 29 

16. What, in relation to physical strength ? 29 

17. What, in relation to physical degeneracy ? .• 29, 30 

18. What, in relation to the importance of exercise ? 30 

19. What is the effect of exercise upon the heart, skin, and appetite ? 30, 31 

20. How does exercise affect the current of the body's circulation ? 31 

21. How does judicious exercise affect the muscles? 31 

22. What is stated of violent and spasmodic exercise ? 31 

23. Of the exercise of walking ? 31 , 32, 33 

24. Of running, leaping, and other modes of exercise ? 3-2 

25. Of physical culture, in connection with out-door exercises ? 33 

26. Of the importance of gymnastics in our schools and colleges ? 33, 34 

27. Of the importance of rest from labor or exercise ? 38, 39 

28. What processes take place during sleep ? 39 

29. What effects follow insufficient sleep ? 3?> 



THE INTEGUMENT, OR SKIN. 41 



chapter iii. 
The Integument, or Skin. 

The Integument — Its Structure — The Nails and Hair — The Complexion 
— The Sebaceous Glands — The Perspiratory Glands — Perspiration 
and its Uses — Importance of Bathing — Different kinds of Baths — 
Manner of Bathing — The Benefits of the Sun — Importance of Warm 
Clothing — Poisonous Cosmetics. 

1. The Integument. — The skin is the outer covering 
of the body. The parts directly beneath it are very sensi- 
tive, and require protection. This is shown whenever by 
accident the skin is broken, pierced, or torn off, the bared 
surface being very tender, and painful to the touch. Nature 
has provided the body with a garment that is soft, pliable, 
close-fitting, and very thin, and yet sufficiently strong to 
enable us to come in contact with the objects that sur- 
round us, without inconvenience or suffering. 

2. The Structure of the Skin. — When examined with 
the aid of the microscope, the skin is found to be made up 
of two layers — the outer and the inner. The inner one is 
called the cutis, or true skin ; the outer one is the epider- 
mis, or scarf-skin. The latter is also known as the cuticle. 
These two layers are closely united, but they may be sepa- 
rated from each other. This separation takes place when- 
ever, from a burn, or other cause, a blister is formed; 
a watery fluid is poured out between the two layers, and 
lifts the epidermis from the true skin. 

Of the two layers, the cuticle is the thinner in most parts 
of the body, and has the appearance of a whitish mem- 
brane. It is tough and elastic, is without feeling, and does 



1 . What is the skin ? Parts directly "beneath ? What is shown ? 

2. Microscopic examination ? What is the cutis ? The cuticle ? 
How separated ? What further is said of the cuticle ? 



4& THE INTEGUMENT, OR SKIN. 

not bleed, when cut. Examine it more closely, and we observe 
that it is composed of minute flat cells, closely compacted, 
and arranged layer upon layer. 

3. The outer layer is constantly being worn out, and 
falls from the body in the form of very fine scales. It is, 
also, continually forming anew on the surface of the inner 
layer. Its thickness varies in different parts of the body. 
Where exposed to use, it is thick, hard, and horn-like, as 
may be seen on the soles of the feet, or on the palms of the 
hands, especially of those who are accustomed to perform 
much manual labor. This is an admirable provision for 
the increased protection of the sensitive parts below the 
skin against all extraordinary exposure. Even the liabil- 
ities of these parts to injury, are thus kindly provided for 
by "the Hand that made us." 

4. The cutis, or true skin, lies beneath the epidermis, 
and is its origin and support. It is firm, dense, elastic, 
very sensitive, and is freely supplied with blood-vessels. 
It is closely connected with the tissues below it, but may 
be separated by means of a sharp instrument. The surface 
of the cutis is not smooth, but is covered here and there 
with minute elevations, called papilla. These are arranged 
in rows, along fine lines, or ridges, such as those which 
mark the palm and fingers ; their number is about 80 to 
the square line (a line being one-twelfth of an inch). 
These papilla} contain the blood-vessels which carry the 
supply of blood needed by the ever- wasting skin. They 
contain nerves also, and are largely concerned in the 
sense of touch; hence they are particularly abundant 
where the touch is most delicate, as at the ends of the 
fingers. 

5. The Nails and Hair. — These are appendages of the 

3. Wearing out of the cuticle ? What then ? Variety in thickness of cuticle ? 
How accounted for? 

4. Location and office of the cutis? What further is said of it? Papillae? 
Touch ? 

5. What are the nails and hair ? The growth of the nail ? The rapidity of its 
growth ? Accident to the nail ? 



THE INTEGUMENT, OR SKIN. 



43 



skin, and although very unlike the cuticle as it appears on 
the surface of the body, they are, in reality, modified forms 
of that layer of the skin. The nail grows from a fold of 
the cuticle at the root, and from the under surface. As 
fast as it is formed, it is 
constantly being pushed 
outward. The rapidity of 
its growth can be ascer- 
tained by filing a slight 
groove on its surface, and 
noticing how the space be- 
tween it and the root of 
the nail increases, in the 
course of a few weeks. 
When the nail is removed 
by any accident, it will be 
replaced by a new one, if 
the root be not injured. 

6. The hairs are pro- 
duced in a similar manner ; 
the skin forming depres- j 
sions, or hair sacs, from 
the bottom Of which they 
grow and are nourished (Fig. 14). They are found, of 
greater or less length, on almost all parts of the surface, 
except the palms of the hands and soles of the feet. On 
certain parts of the body, they grow to great length ; on 
other parts they are so short, that they do not rise beyond 
the hair sac in which they originate. 

7. The bulb, or root, from which the hair arises, is 
lodged in a small pouch, or depression in the skin. The 
shaft is the part which grows out beyond the level of the 
skin. Its growth is altogether in one direction, in length 
alone. The outer part of the hair is quite firm, while its 




Fig. 14. 

a, b. The Root op a Hair. 

, 3. The skin forming the hair sac. 4. I 

baceous glands. 5. The hair sac. 

c. Transverse Section of a H._ir. 



6. How are the hairs produced ? Difference in their length ? 

7. Root of the hair ? Shaft ? Firmness and softness of the hair? 



44 THE INTEGUMENT, OR SKIN. 

interior is softer, and probably conveys the fluids by which 
it is nourished. The hair is more glossy in health than at 
other times. 

8. The nail serves as a protection to the end of the 
finger, and also enables us to grasp more firmly, and to 
pick up small objects. The hair, too, is a protection to 
the parts it covers. On the head, it shields the brain from 
extremes of heat and cold, and moderates the force of blows 
upon the scalp. On the body, it is useful in affording a 
more extensive surface for carrying off the perspiration. 

9. Complexion. — In the deeper cells of the cuticle 
lies a pigment, or coloring matter, consisting of minute- 
colored grains. On this pigment complexion depends; and,, 
according as it is present in less or greater amount, occa- 
sions the difference of hue, that exists between the light 
and dark races of men, and between the blonde and bru- 
nette of the white races. Freckles are due to an irregular 
increase of coloring matter. 

10. The sun has a powerful influence over the develop- 
ment of this pigment, as is shown by the swarthy hue of 
those of the white race who have colonized in tropical 
climates. It is also well illustrated by the fact, that 
among the Jews who have settled in northern Europe, 
there are many who are fair complexioned, while those 
residing in India, are as dark as the Hindoos around them* 

11. An Albino is a person who may be said to have no 
complexion : that is, there is an entire absence of coloring 
matter from the skin, hair, and iris of the eye. This con- 
dition more frequently occurs among the dark races, and 
in hot climates, although it has been observed in almost 
every race and clime. 

12. Sebaceous Glands. — There are in the skin certain 

8. Office of the nail? Of the hair? Give the illustrations. 

9. On what does the complexion depend ? Light and dark races ? Freckles t 

10. Influence of the sun ? How illustrated? Jews? 

1 1 . What is an Albino ? Where are Albinos found ? 

12. What are sebaceous glands ? How do they act? Sebaceous glands of the 
face ? How do they act ? 



THE INTEGUMENT, OR SKIN. 45 

small glands, which produce an oily substance, called se- 
baceous matter. These glands are little rounded sacs, 
usually connected with the hair-bulbs; and upon these 
bulbs, they empty their product of oil, which acts as a 
natural and adequate dressing for the hair (4, Fig. 13). A 
portion of the sebaceous matter passes out upon the sur- 
face, and prevents the cuticle from becoming dry and hard. 
The glands situated upon the face and forehead, open 
directly upon the skin. In these, the sebaceous matter is 
liable to collect, and become too hard to flow off naturally. 

13. These glands on the face and forehead frequently 
appear, on the faces of the young, as small black points, 
which are incorrectly called "worms." It is true, that oc- 
casionally living animalcules are found in this thickened 
sebaceous matter, but they can only be detected by the aid 
of the microscope. This sebaceous matter acts not only to 
keep the skin flexible, and furnish for the hair an oily 
dressing, but it especially serves to protect the skin and 
hair, from the acridity arising from the perspiration. 

14. The Perspiratory Glands. — The chief product 
of the skin's action is the perspiration. For the forma- 
tion of this, there are furnished countless numbers of 
little sweat-glands in the true skin. They consist of fine 
tubes, with globe-like coils at their deeper extremity. Their 
mouths or openings may be seen with an ordinary magnifying 
glass, upon the fine ridges which mark the fingers. These 
tubes, if uncoiled, measure about one-tenth of an inch in 
length. In diameter, they are about one three-hundredth 
of an inch, and upon certain parts of the body there are not 
far from three thousand of these glands to the square inch. 
Their whole number in the body is, therefore, very great; 
and, in fact, it is computed if they were all united, end to end, 
their combined measurement would exceed three miles. 

13. Black points, called worms? Animalcules? Service performed by seba- 
ceous matter ? 

14. Perspiration? Sweat glands? Of what do they consist? Dimension of 
the tubes? 



46 THE IKTEGUMEKT, OR SEEN". 

15. The Sensible and Insensible Perspiration. — 

The pores of the skin are constantly exhaling a watery 
fluid; but, under ordinary circumstances, there is no 
moisture apparent upon the surface, for it evaporates as 
rapidly as it is formed. This is called insensible perspira- 
tion. Under the influence of heat or exercise, however, 
this fluid is excreted more abundantly, and appears on the 
surface in the form of minute, colorless drops. It is then 
termed sensible perspiration. 

16. Water is the chief component of this fluid, there 
being about ninety-eight parts of water to two parts of 
solid matter. The quantity escaping from the body varies 
greatly, according to the temperature of the air, the 
occupation of the individual, and other circumstances. 
The average daily amount of this excretion, in the adult, 
is not far from thirty ounces, nearly two pints, or more 
than nine grains each minute. 

17. The Uses of the Perspiration. — Besides liber- 
ating from the blood this large amount of water, with the 
effete matter it contains, the perspiration serves to regulate 
the temperature of the body. That is to say, as evapora- 
tion always diminishes temperature, so the perspiration, as 
it passes off in the form of fine vapor, cools the surface. 
Accordingly, in hot weather this function is much more 
active, and the cooling influence increases in proportion. 
When the air is already charged with moisture, and does 
not readily receive this vapor of the body, the heat of 
the atmosphere apparently increases, and the discomfort 
therefrom is relatively greater. 

18. The importance of this excretion is shown by the 
effects that often follow its temporary interruption, namely, 
headache, fever, and the other symptoms that accompany 

1 5. What ie sensible perspiration ? Insensible perspiration ? 

16. Components of perspiration? Upon what does perspiration depend? 
Amount of perspiration daily ? 

17. What does perspiration set free from the blood ? What other service does 
perspiration perform ? Explain the process. 

18. Effect of interruption of excretion ? What experiments are mentioned ? 



THE INTEGUMENT, OR SKIN". 47 

''taking cold/' When the perspiration is completely 
checked, the consequences are very serious. Experiments 
have been performed upon certain smaller animals, as rab- 
bits, to ascertain the results of closing the perspiratory 
tubes. When they are covered by a coating of varnish 
impervious to water and gases, death ensues in from six to 
twelve hours ; the attendant symptoms resembling those 
of suffocation. 

19. It is related that, at the coronation of one of the 
Popes about three hundred years ago, a little boy was 
chosen to act the part of an angel : and in order that his 
appearance might be as gorgeous as possible, he was cov- 
ered from head to foot with a coating of gold foil. He was 
soon taken sick, and although every known means were 
employed for his recovery, except the removal of his fatal 
golden covering, he died in a few hours. 

20. The Importance of Bathing. — From these con- 
siderations, it is evident that health must greatly depend 
upon the free action of the skin. " He who keeps the skin 
ruddy and soft, shuts many gates against disease." When 
the watery portion of the perspiration evaporates, the solid 
matter is left behind on the surface. There, also, remain 
the scales of the worn-out cuticle, and the excess of seba- 
ceous matter. In order to secure the natural action of the 
skin, these impurities require to be removed by the frequent 
application of water. 

21. In warm climates, and during hot weather, ablution 
should be more frequently practised. For a person in 
good health, a daily cold bath is advisable. To this should 
be added occasionally a tepid bath, with soap, water alone 
not being sufficient to remove impurities of a greasy nature. 
Soap facilitates this, by forming with such substances a 
chemical mixture, which is readily soluble in water, and is 
by it removed from the body. 

19. Give the story in relation to the boy covered with gold foil. 

20. Give the quotation. Perspiration ? 

2 1 . Ablution in warm climates ? What advice is given ? 



48 THE INTEGUMENT, OR SKIN. 

22. There is a maxim by the chemist Liebig, to the effect, 
that the civilization of a nation is high, in proportion to 
the amount of soap that it consumes ; and that it is low, in 
proportion to its use of perfumes. In some degree, we may 
apply the same test to the refinement of an individual. 
The soap removes impurity; the perfume covers, while 
retaining it. 

23. The different kinds of Baths. — All persons are 
not alike able to use the cold bath. When the health is 
vigorous, and the system does not feel a shock after such a 
bath, a prompt reaction and glow upon the surface will 
show that it is beneficial. Where this pleasurable feeling- 
is not experienced, but rather a chill and sense of depres- 
sion ensues, we are warned that the system will not, 
with impunity, endure cold bathing. 

24. It should also be borne in mind, that the warm or hot 
bath cannot be continued so long, or repeated so frequently 
as the cold, on account of the enervating effect of unusual 
heat so applied to the body. For persons who are not in 
robust health, one warm bath each week is sufficient ; this 
class should be careful to avoid every extreme in reference 
to bathing, clothing, and whatever greatly affects the action 
of the skin. 

25. Sea-bathing is even more invigorating than fresh- 
water bathing. Those who cannot endure the fresh water, 
are often benefited by the salt-water baths. This may be 
accounted for, in part, by the stimulant action upon the 
surface, of the saline particles of the sea- water; but the 
exciting scenes and circumstances of sea-bathing also exert 
an important influence. The open-air exercise, the rolling 
surf, the genial weather, and usually the cheerful company, 
add to its intrinsic benefits. 



22. Liebig's maxim ? What further is added ? 

23. What is said about cold bathing? 

24. What is said about warm bathing ? 

25. What is said about sea-bathing ? 



THE IKTEGUMEin', OR SKIN". 49 

26. Time and Manner of Bathing. — A person in 
sound health may take a bath at almost any time, except 
directly after a full meal. The most appropriate time is 
about three hours after a meal, the noon-hour being proba- 
bly the best. For the cold bath, taken rapidly, no time is 
better than immediately after rising. Those beginning the 
use of cold baths should first try them at 70° Fahr., and 
gradually use those of a lower temperature. From five to 
twenty minutes may be considered the proper limit of time 
to remain in a bath ; but a sensation of chilliness is a signal 
to withdraw instantly, whether at home, or at the sea-side. 
Two sea-baths may be taken daily ; one of any other kind 
is sufficient. 

27. The body should be warm, rather than cold, when 
stepping into the bath; and after it, the skin should be 
thoroughly dried with a coarse towel. It is best to continue 
friction until there is a sensation of warmth or "glow" 
throughout the entire surface. This reaction is the test 
of the good effects of the bath. If reaction is still incom- 
plete, a short walk may be taken, especially in the sunshine. 
It is very congenial, however, both to health and comfort, 
to rest for a short time directly after bathing, or to take 
some light refreshment. This is better than severe exer- 
cise or a full meal. 

28. Bathing among the Ancients. — The Eomans 
and other nations of antiquity made great use of the 
vapor-bath as a means of preserving the health, but more 
particularly as a luxury. Their method was not unlike 
that employed in northern Europe at the present day. 
The public baths of Eome and other cities are among the 
grandest and most interesting monuments of ancient 
luxury and splendor ; and from their ruins have been re- 
covered some of the most beautiful works of art. 



26. What is said as to the time and manner of bathing ? 

27. Condition of the body when bathing ? Direction, after bathing ? 
28* Bathing among the ancients ? Baths of Rome? 



50 THE INTEGUMENT, OR SKIN. 

29. The Thermae, as the baths of Rome were called, 
were of great extent, built very substantially, and orna- 
mented at vast expense. They were practically free to all, 
the cost of a bath having been less than a cent. It is 
related that some persons bathed seven times a day. After 
the bath their bodies were anointed with perfumed oil. If 
the weather was fine, they passed directly from the Thermae 
into the gymnasium, and engaged in some gentle exercise 
previous to taking the midday meal. Between two and 
three in the afternoon was the favorite hour for this ancient 
luxury. Swimming was a favorite exercise, and a knowl- 
edge of it was regarded as necessary to every educated man. 
Their common expression, when speaking of an ignorant 
person, was, " He can neither read nor swim." 

30. The Sun-Bath. — Some also were accustomed daily 
to anoint themselves, and lie or walk in apartments ar- 
ranged for the purpose, with naked bodies exposed to the 
direct rays of the sun. There is an interesting allusion to 
this practice, in a letter of the younger Pliny to the his- 
torian Tacitus, describing the destruction of Pompeii by 
an eruption of Vesuvius. " My uncle," (Pliny the elder,) 
"was at that time in command of the fleet at Misenum. 
On the 24th of August, about one in the afternoon, my 
mother desired him to notice a cloud which seemed of un- 
usual shape and dimensions. He had just returned from 
taking the benefit of the sun, and after a cold bath, and a 
slight repast, had retired to his study." Then follows a 
description of the destruction of Pompeii, and the death 
of the elder Pliny. 

31. We may judge somewhat of "the benefits of the 
sun," by observing the unnatural and undeveloped condi- 
tion of plants and animals which are deprived of light. 
Plants become blanched and tender ; the fish of subterra- 



29. After the bath ? Swimming among the ancients ? 

30. The Sun-bath ? The story of PJiny ? 

3 1 . Benefit of the sun T Effect upon plants ? Ski* f 



THE INTEGUMENT, OR SKIN. 51 

nean lakes, where no light enters, are undersized, and have 
no eyes; tadpoles kept in the dark do not develop into 
frogs; men growing up in mines are sallow, pale, and 
deformed. Besides the well-known effect of solar light in 
tanning the skin, it also makes it thicker and better able 
to resist exposure; though the complexion may be thereby 
injured, the health gains more than compensates for the 
loss of beauty. " To make good the loss of the lily, where 
the sun has cast his ray, He seldom fails to plant the rose." 

32. Clothing. — In reference to clothing, we are far 
more apt, in our changeful climate, to use too little than 
too much. An aphorism of Boerhaave, worth remember- 
ing, if not of adopting, is, " We should put off our winter 
clothing on midsummer's day, and put it on again the day 
after." He also says, " Only fools and beggars suffer from 
the cold ; the latter not being able to get sufficient clothes, 
the others not having the sense to wear them." The prac- 
tice of exposing the limbs and necks of young children, 
for the alleged purpose of "hardening" them, is quite 
hazardous. It is not to be denied that some seem to be 
made tough by the process ; but it is so only with the rugged 
children, the delicate ones will invariably suffer under this 
fanciful treatment. As has been stated before, the skin is 
constantly acting, by night as well as by day. It is there- 
fore conducive both to cleanliness and comfort to change 
entirely the clothing on retiring for the night. The day- 
clothing should be aired during the night, and the bedding 
should be aired in the morning, for the same reason. 

33. Poisonous Cosmetics. — The extensive use of 
cosmetics for the complexion is a fertile source of disease. 
The majority of these preparations contain certain poison- 
ous mineral substances, chiefly lead. Now, the skin 
rapidly absorbs the fine particles of lead, and the system 



32. Direction about clothing? Exposing limbs of children? Clothing, night, 
and day ? 

33. Cosmetics ? Painters' colic? 



bZ THE INTEGUMENT, OR SKIN. 

experiences the same evil effects that are observed among I 
the operatives in lead works and painters, namely, " paint- 
ers' colic," and paralysis of the hands, called " wrist-drop." 
34. Certain hair-dyes also contain lead, together with 
other noxious and filthy ingredients. These do not work 
as great harm as the cosmetics, since they are purposely 
kept away from the skin, but they rob the hair of its 
vitality. Eye-washes, too, are made from solutions of lead, 
and many an eye has been ruined by their use. They de- 
posit a white metallic scale on the surface of the eye, which 
becomes a permanent obstruction to the vision. 



QUESTIONS FOR TOPICAL REVIEW. 

PAGE 

1. What are the characteristics of the skin, and what office does it perform ? 41 

2. What can you state of the structure of the skin ? 41 

3. Describe the cuticle and tell its use 41, 42 

4. Describe the cutis or true skin and tell its use 42 

5. What can you state of the nature and growth of the nail ? 42, 43 

6. Of the nature and growth of the hair ? 42, 43, 44 

7. Of the offices performed by the nails and hair ? 44 

8. How is the difference in complexion in different persons accounted for?. 44 

9. How is the presence of freckles accounted for ? 44 

10. How does Nature provide a dressing for the hair ? 44, 45 

11. What other service do the sebaceous glands perform ? 45 

12. State what you can of the perspiratory glands 45 

13. What is the difference between sensible and insensible perspiration ?. . . 46 

14. State the uses and importance of perspiration 46, 47 

15. What impurities gather naturally on the skin ? 47 

16. Repeat what is said of the importance of bathing 47, 48 

17. When should we indulge in cold, warm, and sea bathing ? 48, 49 

18. What is the effect in each case ? '. 48 

19. What directions are given as to the time and manner for bathing ? 49 

20. What is related of bathing among the ancients ? 49, 50 

21. What is related to show the antiquity of sun-bathing ? 50 

22. What are the effects of sun-bathing ? 50, 51 

23. What directions are given in relation to clothing the body ? 51 

24. What can you state of poisonous cosmetics ? 51, 52 

25. Of hair-dyes and eye-washes ? 52 






THE CHEMISTRY OF FOOD. 53 






chapter iv. 

The Chemistry of Food. 

The Source of Food — Inorganic Substances — Water — Salt — Lime — Iron 
— Organic Substances — Albumen, Fibrin, and Casein — The Fats or 
Oils — The Sugars, Starch, and Gum — Stimulating Substances — 
Necessity of a Regulated Diet. 

1. The Source of Food. — The term /ootf includes all 
those substances, whether liquid or solid, which are neces- 
sary for the nourishment of the body. The original source 
of all food is the earth, which the poet has fitly styled the 
" Mother of all living." In her bosom, and also in the air, 
are contained all the elements on which life depends. But 
man is unable to obtain nourishment directly from suc^ 
crude chemical forms as he finds in the inorganic world. 
They must, with a few exceptions, be prepared for his use, 
by being transformed into new and higher combinations, 
more closely resembling the tissues of his own body. 

2. This transformation is effected, first, by the vegetable 
world. But all plants are not alike useful to man ; while 
some are absolutely hurtful. Accordingly, he must learn 
to discriminate between that which is poisonous and that 
which is life-supporting. Again, all parts of the same 
plant or tree are not alike beneficial: in some, the fruit, 
in others, the leaves, and in others, the seeds only are 
sufficiently refined for his use. These he must learn 
to select; he must also learn the proper modes of prepay 
ing each kind for his table, whether by cooking or othe: 
processes. 



1 . The term food ? Source of food ? Need of preparing food ? 

2. Usefulness and hurtfulneee of plants ? What then must man do ? Parte of 
the same plant or tree ? 



54 THE CHEMISTRY OF FOOD. 

3. Again, certain forms of the vegetable creation which 
are unfit, in their crude state, for man's food, and which he 
rejects, are chosen as food by some of the lower animals, 
and are, by them, made ready for his use. Thus the bee 
takes the clover, that man cannot eat, and from it collects 
honey. The cattle eat the husks of corn and the dried 
grass, that are by far too coarse for man, and in their own 
flesh convert them into tissues closely resembling his mus- 
cular tissue. In this way, by the aid of the transforming 
processes of the vegetable and animal creations, the simple 
chemical elements of the mineral kingdom are elaborated 
into our choice articles of food. 

4. Inorganic Substances. — The substances we use as 
food are classified as organic and inorganic. By organic 
substances are meant those derived from living forms, such 
as vegetables and animals. Inorganic substances are those 
simpler inanimate forms which belong to the mineral 
kingdom. The former alone are commonly spoken of as 
food, but the latter enter very largely into the constitution 
of the body, and must therefore be present in our food. 
With the exception of two articles, water and common 
salt, these substances only enter the system when blended 
with organic substances. 

5. Water. — Water, from a physiological point of view, is 
the most important of all the articles of food. It is every- 
where found in the body, even in the bones and the teeth. 
It has been computed that as large a proportion as two- 
thirds of the body is water. The teeth, the densest of the 
solids in the human system, contain ten per cent, of water. 
The muscles, tendons, and ligaments are more than half 
water; for it is found that they lose more than half their 



3. Certain forms of vegetable creation? Example of the bee ? Cattle? The 
inference ? 

4. What classification ? Define organic substances. Inorganic. Organic, 
how spoken of? The inorganic ? Water and salt ? 

5. Water in physiology ? Where found ? Computation? Water in the teeth ? 
Muscles, tendons, and ligaments ? How ascertained? Water in the fluids of the 
body ? What is the advantage ? 



THE CHEMISTRY OF FOOD. 55 

weight when dried with moderate heat. But it is in the 
fluids of the body that water is found most abundantly. 
It gives to them the power of holding a great variety of 
substances in solution, and is the great highway by which 
new supplies are conveyed to the point where they are 
required, and by which old particles of matter, that have 
served their uses, are brought to the outlets of the body to 
be thus removed from the system. 

6. Man can remain a longer time without solid food 
than without water. He may be deprived of the former 
for ten to twelve hours without great suffering, but depri- 
vation of water for the same length of time will produce 
both severe pain, and great weakness. The food should contain 
not less than two parts of water to one of solid nutriment. 
Water constitutes the great bulk of all our drinks, and is 
also a large constituent of the meats, vegetables, and fruits 
which come upon the table. Fruits, especially, contain it 
in great abundance, and ? in their proper season, furnish 
most agreeable and refreshing supplies of the needed fluid. 

7. Common Salt. — Salt, or sodium chloride, as an 
article of food, is obtained chiefly from the mineral king- 
dom; although plants contain it in small quantities, and 
it is also found in the tissues of nearly all animals used 
as food. In the human body, it is an ingredient of all 
the solids and fluids. The importance of salt to animal 
life in general, is «fcown by the great appetite for it mani- 
fested by domestic animals, and also by the habitual resort 
of herds of wild beasts to the "salt-licks" or springs. In 
those parts of the world where salt is obtained with diffi- 
culty, man places a very high price upon it. 

8. Experiments upon domestic animals show that the 
withdrawal of salt from their food, not only makes their 



6. Length of time man can do without food or water ? Give the comparison ? 
Bulk of drinks ? Constituent of meats, etc. ? Fruits ? 

7. Salt, how obtained ? Where found? In the human body? Importance of 
salt ? What else can you state of the value of salt? 

8* Experiments upon animals ? 



56 THE CHEMISTRY OP FOOD. 

hides rough and causes the hair to fall out, hut also inter- 
feres with the proper digestion of food. If it he withheld 
persistently, they become entirely unable to appropriate 
nourishment, and die of starvation. 

9. Salt is usually taken into the system in sufficient 
quantities in our food. Even the water we drink often 
has traces of it. The habitual use of much salt in cook- 
ing, or as a seasoning at the table, is not wise; and while 
it may not lead to consumption, as some writers declare, it 
is a bad habit in itself, and leads to the desire for other and 
more injurious condiments. 

10. Lime. — This is the mineral substance which we 
have spoken of before as entering very largely into the com- 
position of the bones. It is the important element which 
gives solidity and permanence to the framework upon 
which the body is built. Calcium tri-phosphate, or "bone- 
earth," is the chief ingredient of the bones and teeth, but 
is found in the cartilages and other parts of the body in 
smaller quantities. 

11. How does this substance find its way into the body? 
Meat, milk, and other articles obtained from the animal 
kingdom contain it, and it is abundantly stored away also, 
in the grains from which our bread is made, in wheat, rye, 
and Indian corn. In early life, while the body is growing,, 
the supplies of this substance should be carefully provided. 
The evil effects of the deprivation of it are too often and 
painfully evident in the softening of the bones, and in the 
predisposition to curvature of the spine — deformities which 
are most deplorable and which continue through life. 

12. Iron. — This substance is probably the most abun- 
dant and widely diffused of the metals. It is found in 



9. Salt, how taken into the system ? Its use in cooking ? Consumption ? 

10. Lime in the bones ? What does it impart ? Chief ingredient of the bones 
and teeth ? Where else found ? 

1 1 . How does lime find its way into the body ? Early life ? Effect of its 
deprivation? 

12. Iron, its abundance and diffusion ? Where found? What part of the blood 
is it ? How supplied to the system ? In case of loss of blood or wasting disease ? 



THE CHEMISTRY OF FOOD. 57 

most of the vegetables, and is a very important component 
of animal tissues. It enters into the composition of hu- 
man blood in about one part per thousand. Ordinarily, 
the food conveys to the system enough iron for its use, but 
it must sometimes be introduced separately as a remedy, 
especially after great loss of blood, or after some wasting 
disease. Under its influence the blood seems to be 
rapidly restored, and a natural color of the lips and skin 
replaces the pallor caused by disease. 

13. Other Inorganic Substances. — In addition to 
the substances mentioned, the mineral kingdom supplies 
compounds of soda, potash, and magnesia, which are es- 
sential for the use of the body. They occur in small 
quantities in the body, and enter it in combination with 
the various articles of diet. 

14. Organic Substances. — These substances are derived 
from the vegetable and animal creations. They comprise 
all those articles which are commonly spoken of as " food," 
and which are essential to sustain the body in life and 
strength. They are divided into three groups, namely: 
the Albuminoid substances, the Fats, and Sugars. 

15. The Albuminoids. — This class includes three im- 
portant nutritive substances — (1) Albumen, which gives it 
its name; (2) Fibrin, including gluten; and (3) Casern. 
These compounds constitute a large part of the human 
body, and the food contains them in proportionally large 
quantities. Their importance is so great, and the system 
so promptly suffers from their absence, that they have been 
styled the " nutritious substances." The properties which 
they hold in common are, that they do not crystallize, and 
have a jelly-like form, except when heat is applied to them, 
when they harden, or coagulate. 



13. Soda, potash, and magnesia ? How do they occur ? 

14. Organic substances, whence derived ? What do they comprise ? Groups ? 

15. The Albuminoid class, includes what? These compounds constitute 
what ? The food ? Their importance ? Their properties ? 



58 THE CHEMISTRY OF FOOD. 

16. They likewise decompose, or putrefy, under the influ- 
ence of warmth and moisture. Hence the decay of all 
dead animal tissues. Cold arrests this process. It is well 
known that milk, eggs, and the like, " keep" much longer 
in winter than at other seasons. The bodies of elephants, 
caught in the ice many hundred years ago, are occasion- 
ally borne by the icebergs to the coast of Siberia, com- 
pletely frozen, but preserved almost perfectly in form and 
limb. 

17. Albumen exists in milk, meat, the grains, and the 
juices of many plants ; but the purest form is obtained 
from the white of egg. When we consider that an egg is 
composed chiefly of albumen and water — namely, six parts 
in seven; and when we also consider the numerous, diverse, 
and complex tissues — the muscles, bones, internal organs, 
bill, claws, and feathers — with which the chick is equipped 
on leaving his shell, we are impressed with the importance 
of these apparently simple constituents of the food and 
body. 

18. Fibrin is derived from meats, and exists in the 
blood both of man and the lower animals. Gluten, or 
vegetable fibrin, resembles closely true fibrin, and is abun- 
dantly furnished in wheat and other grains from which 
flour is commonly made. Animal fibrin coagulates spon- 
taneously when it is removed from the body, and thus 
causes the " clotting" of the blood. 

19. Casein is the curdy ingredient of milk, and a highly 
important food-substance. Its coagulation in milk takes 
place not from heat, but by the addition of an acid, and 
also when milk becomes sour from exposure to the air. It 
is commonly effected, however, by introducing a piece of 
rennet, a preparation made from a calf s stomach. The 
curds, or casein, may then be separated from the 



16. Decomposition? Effect of cold ? Illustrations ? Elephants? 

17. In what substances does albumen exist ? What further is said of the eggt 

18. Fibrin, gluten, clotting of the blood ? 

19. Casein ? Its coagulation ? Effect of rennet ? Making of cheese ? 



THE CHEMISTRY OF FOOD. 59 

and made into cheese, by pressing it sufficiently to drive 
off the water. 

20. The Fats or Oils. — This is the second group of 
organic foods. Those which are more solid are called fats : 
the more fluid ones are the oils. Oleaginous substances 
are supplied in both animal and vegetable food ; but, from 
whatever source derived, they are chemically much alike. 
They are insoluble in water, and yet they unite readily 
with the watery fluids of the body, and are by them con- 
veyed to its various parts for their nourishment. This is 
due to their property of "emulsifying;" that. is, they are 
held in suspension, in a finely divided state, in water. Or- 
dinary milk is an example of an emulsion. We know that 
it contains fat ; for butter is obtained from it, and, under 
the microscope, the minute oil-globules may be distinctly 
seen. 

21. In our country and climate, and also in colder 
climates, fatty articles of food are principally derived from 
the animal creation, such as meat or flesh, milk and butter. 
But most of the bread-stuffs contain more or less fat or oil ; 
Indian meal as much as nine parts in a hundred. 

22. Among persons living in cold climates, the appetite 
for oleaginous food is especially eager ; and they require 
large quantities of it to enable them to resist the depress- 
ing influences of cold. Since vegetation is scanty and 
innutritious, and the waters of the frozen regions abound 
in animal life, they must rely wholly upon a diet derived 
from the latter source. The Esquimaux consumes daily 
from ten to fifteen pounds of meat or blubber, a large 
proportion of which is fat. The Laplander will drink 
train-oil, and regards tallow-candles as a great delicacy. 
In hot climates, on the contrary, where flourish the olive 



20. What are the fats ? The oils? How supplied ? How alike? Emulsifying? 
Example ? How do we know it ? 

21 . Whence are fatty articles of food derived? 

22. Appetite of persons in cold climates ? What do they require ? Upon what 
must they rely ? Why ? The Esquimaux ? Laplander ? Olive and palm ? 



60 THE CHEMISTRY OF FOOD. 

and the palm, this kind of food may be obtained from 
vegetable sources in abundant quantities. 

23. The Sugars, or the Saccharine Substances. — 

These constitute the third, and last, group of the organic 
substances, which are employed as food. This group em- 
braces, in addition to the different kinds of Sugar ; the 
varieties of starch and gum, from whatever source derived. 
The two substances last named do not, at first sight, pre- 
sent many points of similarity to sugar ; but they closely 
resemble it in respect to their ultimate chemical composi- 
tion, being made up of the same elements, in nearly the 
same proportions. And their office in the system is the 
same, since they are all changed into sugar by the processes 
of digestion. 

24. Sugar is chiefly of vegetable origin; the animal 
varieties being obtained from honey and milk. The most 
noticeable characteristic of this substance is its agreeable, 
sweet taste, which makes it everywhere a favorite article of 
food. But this quality of sweetness is not possessed by all 
the varieties of sugar in the same degree ; that obtained 
from milk, for instance, has a comparatively feeble taste, 
but rather imparts a gritty feeling to the tongue. The 
other important properties of sugar are, its power to 
crystallize when evaporated from watery solutions, such as 
the juices of many plants ; a tendency to ferment, by which 
process alcohol is produced; and a ready solubility in 
water. This latter quality renders it very easy of digestion, 
and more so than any other of the saccharine group. It is 
computed that the annual production of sugar, in all parts 
of the world, is more than one million of tons. The kind 
of sugar that is in ordinary use, in this country, is prepared 
from the juice of the sugar-cane, which contains eighteen 
per cent, of sugar. In France it is manufactured from the 

23. Which are the third of the organic groups ? What do they embrace ? 
Points of resemblance ? 

24. Origin of the sugars? Ordinary sugar ? Beetroot? Maple-augar? Grape- 
sugar ? Cane-sugar ? 



THE CHEMISTRY OF FOOD. 



oy 



beet root, which holds about nine per cent. ; the maple-tree 
of our climate yields a similar sugar. The sweet taste of 
fruits is due to the presence of grape-sugar: the white 
grains seen on raisins belong to this variety. Cane-sugar 
is more soluble than the latter, and has twice the sweeten- 
ing power. 

25. Starch. — This is the most widely distributed of 
the vegetable principles. 
It is tasteless, inodorous, 
and does not crystallize. 
It consists of minute 
rounded granules, which, 
under the microscope, 
reveal a somewhat uni- 
form structure (Fig. 15). 
Starch will not dissolve 
in cold water, but in 
boiling water the small 
grains burst open, and 
may then be dissolved 
and digested. 

26. The bread stuffs, wheat, corn, and rye flours, are 
more than one-half starch. Eice, which is the " staff of 
life" to one-third of the human family, contains eighty 
per cent. Unripe fruits have much starch in them, 
which renders them indigestible when eaten uncooked; 
for the grains of raw starch are but slightly acted upon 
within the body. But, under the potent chemistry of the 
sun's ray, this crude material is converted into sugar. 
Thus are the fruits prepared by the careful hand of 
Nature, so that when ripe they may be freely used without 
further preparation. 

27. Gum is commonly found in those articles which 

25. Starch, how widely distributed? Its qualities? Its constituents? Its 
solubility ? 

26. How much starch in bread-stuffs ? In rice ? Unripe fruits ? Ripe fruits ? 

27. Gum, where found? Its composition ? Gum Arabic? 




Fig. 15.— Granules of Potato Starch. 



62 THE CHEMISTRY OF FOOD. 

also contain starch ; and has the same chemical composi- 
tion as the latter, but is much less nutritious. In the 
East, gum-arabic and similar substances are largely em- 
ployed as food. Persons who travel by caravan across vast, 
sandy deserts, find such substances well adapted to their 
wants, since they are not perishable, and are easily packed 
and carried. 

28. Stimulating Substances. — The three classes of 
food-principles already considered — the Albuminoids, the 
Fats, and the Sugars — comprise all the more important 
organic ingredients of our food. There are, besides, a 
great variety of coloring and flavoring matters that stim- 
ulate or increase the appetite for food by appealing to the 
eye and taste; but they are not nutritious, and are quickly 
separated from the truly useful substances, and do not 
long remain in the body. Among these may be classed 
spices, flavors of fruits, tea, coffee, and vegetable acids. 

29. Necessity of a Regulated Diet. — A great vari- 
ety of experiments have been tried in order to test the rela- 
tive value of the different nutritive principles. They have 
been practised to some extent upon man, but chiefly upon 
those inferior animals which require a similar diet to man. 

30. By this means it has been demonstrated that — first, 
when any one of these substances is eaten exclusively, the 
body is imperfectly nourished, and life is shortened. Dogs 
fed exclusively upon either albumen, fat, or sugar, soon die 
of starvation. Second, a diet long deprived of either of 
these principles, is a fertile cause of disease; for example, 
on ship-board, where fresh vegetables are not dealt out for a 
long period, scurvy becomes prevalent among the sailors. 
They are, however, to a certain extent mutually convertible, 
and thus the missing article is indirectly supplied. For 



28. The three clashes of food principles ? What besides? What is said of 
them ? Name the articles not nutritions. 

29. What is said of experiments that have .been tried! 

30. What has been demonstrated in the first place? Example? Second de- 
monstration ? Example ? Give the illustration in relation to convertibility. 



THE CHEMISTRY OF FOOD. 



instance, sugar changes to fat in the body; and hence, as 
is well known, the " hands" on a sugar plantation grow 
fat during the sugar season, by partaking freely of the 
ripened juices of the cane. 

31. That is the best diet therefore which contains some 
of each of these principles, in due proportion; and that is 
the worst which excludes the most of them. The cravings 
and experience of man had unerringly guided him to a 
correct regulation of his diet, long before the chemistry 
of food was understood; so that his ordinary meals 
long ago combined these various principles, the necessity 
and value of which are now explained. 



QUESTIONS FOR TOPICAL REVIEW. 

PAGE 

1. What is understood by the term food ? 53 

2. What can you state in relation to the source of food ? 53 

3. What discriminations and selections are necessary ? 53, 54 

4. How can you tell the organic from the inorganic substances ? 54 

5. What relative position does water hold as an article of food ? 54 

6. In what parts of the body is water found ? 54, 55 

7. In what articles that we eat is it found ? 55 

8. If you were required to go without water or solid food for a number of days, 

which would you prefer to have, and why ? 55 

9. What can you state of the importance of salt as an article of food ? 55, 56 

10. How abundant ie salt, and how does it find its way into the human sys- 

tem ? 55, 56 

11. What can you state of the importance of lime in the body ? 56 

32. What, of the importance of iron ? 66, 57 

13. What further is stated of other inorganic substances ? 57 

14. What in relation to organic substances ? 5 ? 

15. What can you 6tate in relation to the albuminoids ? 57, 58 

16. What, in relation to albumen ? M 

17. What, in relation to casein ? 58 ' 59 

18. In relation to the fats or oils, and how generally consumed ? 59, 60 

19. What do we understand by the sugars or saccharine substances ? 60 

20. State what you can of sugar— its origin and various qualities 60, 61 

21. Of starch— its varieties and qualities °1 

22. Of the abundance of starch, and its importance as a food principle 61 

23. What is stated in relation to stimulating substances ? 63 

24. Of the necessity for regulation in diet? 62, 63 



64 FOOD AND DRINK. 



CHAPTER V. 

FOOD AND DRINK. 

Necessity for Food — Waste and Repair — Hunger and Thirst — Amount 
of Food — Renovation of the Body — Mixed Diet — Milk — Eggs — Meat 
— Cooking — Vegetable Food — Bread — The Potato — Fruits — Purity 
of Water — Action of Water upon Lead — Coffee, Tea, and Chocolate 
—Effects of Alcohol. 

1. Necessity for Food. — Activity is everywhere fol- 
lowed by waste. The engine uses up coal and water to 
produce motion, the stream wears away its bank, the 
growing corn-blade draws tribute from the soil. When the 
human body acts, and it is always in action during life, some 
of its particles are worn out and thrown off. This waste 
must constantly be repaired, or the body suffers. In this 
fact is seen the necessity for food. The particles, thus worn 
out, being henceforth useless, are removed from the body. 
Our food and drink are rapidly transformed into a new 
supply of living, useful material, to be in turn used up 
and replaced by a fresher supply. 

2. Waste and Repair. — In this way the healthful 
body, though always wasting, is always building up, and 
does not greatly change in size, form, or weight. At two 
periods of life the processes of waste and repair are not ex- 
actly balanced. In early life the process of building up is 
more active, and in consequence the form is plump, and 
the stature increases. Eepair now exceeds waste. On the 
other hand, when old age comes on, the wasting process is 
more active, the flesh and weight dimmish, the skin falls 
in wrinkles, and the senses become dull. Only during the 
prime of life — from about twenty to sixty years of age — is 
the balance exact between loss and gain. 

1. What follows activity? Examples? Necessity for food ? 

2. Give the theory in relation to waste and repair. 



FOOD AND DRINK. Go 



3. Hunger and Thirst. — When the system is deprived 
of its supply of solid food during a longer time than usual, 
nature gives warning by the sensation of hunger, to 
repair the losses that have taken place. This sensation 
or pain appears to be located in the stomach, but it is really 
a distress of the system at large. Let a sufficient quantity 
of nourishment be introduced into the system in any other 
way than by the mouth, and it will appease hunger just as 
certainly as when taken in the usual manner. 

4. The feeling of thirst, in like manner, is evidence that 
the system is suffering from the want of water. The 
apparent seat of the distress of thirst is in the throat ; but 
the injection of water into the blood-vessels is found to 
quench thirst, and by the immersion of the body in water, 
the skin will absorb sufficient to satisfy the demands of the 
system. The length of time that man can exist without 
food or drink is estimated to be about seven days. If water 
alone be supplied, life will last much longer ; there being 
cases recorded where men have lived twenty days and over, 
without taking any solid food. 

5. Quantity of Food. — The quantity of food required 
varies greatly, according to the individual and his mode of 
life. The young, and others who lead active lives, or who 
live in the open air, require more food than the old, the 
inactive, or the sedentary. Those who live in cold regions 
require more than the inhabitants of hot climates. Habit, 
also, has much to do with the quantity of food required. 
Some habitually eat and drink more than they actually 
need, while a few eat less than they should. 

6. The average daily quantity of food and drink for a 
healthy man of active habits is estimated at six pounds. 
This amount may be divided in about the following pro- 

3 . System deprived of food ? Warning ? What is the pain ? How proved ? 

4. Feeling of thirst? Seat of the pain? How proved? Time a person can 
exist without food ? 

5. Amount of food required? The young and others? Those living in hot 
and cold climates ? Habits ? 

6. Quantity of food daily? How divided? Compare with the weight of the body ? 



06 FOOD AND DRINK. 

portions : the mineral kingdom furnishes three and one- 
half pounds, including water and salt ; the vegetable king- 
dom, one and one-half pounds, including bread, vegetables, 
and fruits; the animal kingdom, one pound, comprising 
meat, eggs, butter, and the like. This quantity is about 
one twenty-fourth the weight of the body, as it is generally 
computed ; the average weight of an adult man being placed 
at 140 pounds. A man, therefore, consumes an amount of 
solid and liquid nutriment every twenty-four days equal 
in weight to that of his body, a corresponding amount 
being excreted, or removed from the system in the same 
time. 

7. Renovation of the Body. — By this process, so far 
as weight is concerned, the body might be renewed every 
twenty-four days; but these pounds of food are not all real 
nutriment. A considerable portion of that which we eat 
is innutritious, and though useful in various ways, is not 
destined to repair the losses of the system. An opinion 
has prevailed that the body is renewed throughout once in 
seven years; how correct this may be it is not easy to 
decide, but probably the renovation of the body takes 
place in a much shorter period. Some parts are very 
frequently renewed, the nutritive fluids changing more or 
less completely, several times during the day. The muscles, 
and other parts in frequent exercise, change often during a 
year ; the bones not so often, and the enamel of the teeth 
probably never changes after being once fully formed. 

8. Mixed Diet. — The habits of different nations in 
respect to diet exhibit the widest and strangest diversity. 
The civilized, cook their food, while savages often eat 
it in a raw state. Some prefer it when fresh, others allow 
it to remain until it has become tainted with decay. 
Those dwelling in the far north subsist almost wholly on 

7. How often then might the hody be renewed? Why is it not? Opinion? 
How correct ? What further is stated ? 

8» Habits of nations ? Give the different cases. 



POOD AND DKINK. 67 

animal food, while those living in hot climates have boun- 
tiful supplies of delicious fruits with which to satisfy all 
their bodily wants. One race subsists upon the banana, 
another upon the blubber of seals. In temperate climates, 
a diet composed partly of vegetable and partly of animal 
food is preferred. 

9. The important point to consider is, however, not one 
of origin, but whether the chemical principles (mentioned 
in the last chapter) enter into the composition of the diet. 
A purely vegetable diet may be selected which would contain 
all the principles necessary to sustain life. It is recorded of 
Louis Cornaro, a Venetian noble, that he supported himself 
comfortably for fifty-eight years on a daily allowance of 
twelve ounces of vegetable food, and about a pint of light 
wine. On the other hand, the food of John the Baptist, 
consisting of "locusts and wild honey," is an example of 
the sustaining power of a diet strictly animal in its origin. 

10. In our climate, those who lead active lives crave an 
allowance of animal food; and it has been found by ex- 
perience that with it they can accomplish more work and 
are less subject to fatigue, than without it. Among na- 
tions where an exclusively vegetable diet is employed, indi- 
gestion is a disorder especially prevalent. 

11. The necessity for occasionally changing or varying 
the diet, is seen in the fact that no single article comprises 
all the necessary principles of food, and that the contin- 
uous use of any one diet, whether salt or fresh, is followed 
by defective nutrition and disease. There is one exception 
to this rule : in infancy, milk alone is best calculated 
to support life ; for then the digestive powers are incom- 
pletely developed, and the food must be presented in the 
simplest form possible. It should also be remembered 



9. The point to consider? Vegetable diet? Louis Cornaro ? John the Bap 
tist? 

1 0. What has been found in our climate ? Exclusive vegetable diet ? 

1 1 . Necessity for change in diet ? Continuous use of the same diet? Excep 
tion? Why? Too rich diet? Horses? 



FOOD AND DRINK. 



that too rich diet is injurious, just as truly as one that is 
inadequate. When the food of horses is too nutritious, in- 
stinct leads them to gnaw the wood-work of their mangers. 

12. Different Articles of Diet— Milk.— Milk is 
the earliest nutriment of the human race, and in the selec- 
tion and arrangement of its constituents, may be regarded 
as a model food, no other single article being capable of 
sustaining life so long. Cow's milk holds casein, one of 
the albuminoids, about five parts in one hundred ; a fatty 
principle, when separated, known as butter, about four 
parts; sugar of milk four parts; water and salts eighty- 
seyen parts. The casein and fatty substance are far more 
digestible in milk, than after they have been separated 
from it in the form of cheese and butter. 

13. Since milk, in itself, is so rich an article of food, 
the use of it as a beverage is unwise, unless the quantity 
of the other articles consumed be reduced at the same 
time. The milk sold in cities is apt to be diluted with 
water. The way to detect the cheat is by testing the 
specific gravity of the article. Good milk is about 1030; 
skimmed milk 1035; but milk diluted one-fifth is 1024. 
An instrument called the lactometer is also used, by 
which the amount of cream present is ascertained. 

14. Eggs. — An egg is about two-thirds water, the bal- 
ance is pure albumen and fat in nearly equal proportions. 
The fat is in the yolk, and gives it its yellow color. Eggs 
contain none of the sugar-principles, and should be eaten 
with bread or vegetables that contain them. Soft-boiled 
eggs are more wholesome than those which are hard-boiled 
or fried, as the latter require longer time to digest. 

15. Meats. — The meats, so called, are derived from the 
muscular parts of various animals. They are most im- 



1 2. Milk as a model food ? Cow's milk ? The constituents when separated ? 

1 3. Milk as a beverage ? Milk sold in cities ? How to detect the cheat ? 

14. Composition of eggs? Yolk? How should eggs be eaten ? Why? How 
boiled? Why? 

15. Meats, whence derived ? Why important ? Flesh of young animals ? 



FOOD AND DRINK. 69 



portant articles of food for adults, inasmuch as they are 
richly stored with albuminoid substances, and contain 
more or less fat. Such food is very nourishing and easily 
digested if eaten when fresh, — veal and pork being excep- 
tions. The flesh of young animals is more tender and, in 
general, more digestible than that of older ones. All meat 
is more tough immediately after the killing of the animal, 
but improves by being kept a certain length of time. 

16. Some persons prefer flesh that has begun to show 
signs of decomposition, or is unmistakably putrid. By 
some, venison is not considered to have its proper flavor 
until it is tainted. In England, people prefer mutton 
that is in a similar condition, just as on the continent of 
Europe many delight in cheese that is in a state of decom- 
position. In certain less civilized countries flesh is not only 
eaten uncooked, but in a mouldy, rotten condition. The 
use of such food is not always immediately injurious, but 
it predisposes to certain diseases, as indigestion and fevers. 

17. Cold is one means of preserving meat from decay. 
In the markets of northern Russia, the frozen carcases of 
animals stand exposed for sale in the winter air for a con- 
siderable time, and are sawn in pieces, like sticks of wood, 
as the purchases are made; such meat, when thawed, 
being entirely fit for food. Beef and pork are preserved 
by salting down in brine, and in this condition may be 
carried on long voyages or kept for future use. Salted 
meat is not as nutritious as fresh, since the brine absorbs 
its rich juices and hardens its fibres. Long continued use 
of salt meats, without fresh vegetables, gives rise to the 
disease called scurvy, formerly very prevalent on ship- 
board and in prisons. 

18. Cooking. — The preparation of food by the agency 



1 6. Preference of persons ? Venison ? Mutton ? Cheese ? Uncooked flesh ? 

17. Cold as a preserver ? Meat in Russia? Beef and pork, how preserved? 
Salted meat as food ? Scurvy ? 

18. The antiquity of the custom of cooking food? Object of cooking? The 
oyeter ? Raw meat ae an occasional food ? 



70 FOOD A2s T D PRIKK. 



of fire is of almost universal practice, even among the 
rudest nations. The object of cooking is to render food 
more easy of digestion by softening it, to develop its 
flavor, and to raise its temperature more nearly to that of 
the body. A few articles of flesh-food are eaten un- 
cooked in civilized lands, the oyster being an instance. 
Eaw meat is occasionally eaten by invalids with weak 
digestive powers, and by men training for athletic con- 
tests. 

19. In boiling meat, the water in which it is placed 
tends to dissolve its nutrient juices. In fact, the cooking 
may be so conducted as to rob the meat of its nourish- 
ment, its tenderness, and even of its flavor. The proper 
method, in order to preserve or promote these qualities, is 
to place the meat in boiling water, which, after a few 
minutes, should be reduced in temperature. In this way 
the intense heat, at first, coagulates the exterior layers of 
albumen, and imprisons the delicate juices; after that, 
moderate heat best softens it throughout. When soup is 
to be made, an opposite course should be pursued; for 
then the object is to extract the juices and reject the fibre. 
Meat, for such purpose, should be cut in small pieces and 
put into cold water, which should then be gradually raised 
to boiling heat. 

20. Eoasting is probably the best method of cooking 
meat, especially "joints" or large pieces, as by this process 
the meat is cooked in its own juices. Eoasting should 
begin with intense heat, and be continued at a moderate 
temperature, in order to prevent the drying out of the 
nutritious juices, as by this process an outer coating or 
crust of coagulated albumen is formed. During this pro- 
cess the meat loses one-fourth of its weight, but the loss 
is almost wholly water, evaporated by the heat. Too 

, 19. Effect of boiling meat? How may the cooking be done? The proper 
method? Effect? Making of soup ? 
20. Roasting ? How should it be done ? Give the philosphy of the process. 



FOOD AND DRINK. 71 

intense or prolonged heat will dry the meat, or burn it. 
Frying is the worst possible method, as the heated fat, by 
penetrating the meat, or other article placed in it, dries 
and hardens it, and thus renders it indigestible. 

21. Trichina. — It should be remembered that ham, 
sausages, and other forms of pork, should never be eaten 
in a raw or imperfectly cooked condition. The muscle of 
the pig is often infested by a minute animal parasite, or 
worm, called trichina spiralis. This worm may be intro- 
duced alive into the human body in pork food, where it 
multiplies with great rapidity, and gives rise to a painful 
and serious disease. This disease has been prevalent in 
Germany, and cases of it occur from time to time in this 
country. 

22. Fish. — The part of fish that is eaten is the muscle, 
just as in the case of the meats and poultry. It closely 
resembles flesh in its composition, but is more watery. 
Some varieties are very easy of digestion, such as salmon, 
trout, and cod; others are quite indigestible, especially 
lobsters, clams, and shell-fish generally. A diet in which 
fish enters as the chief article, is ill adapted to strengthen 
mind or body, while its continued use is said to be the 
fertile source of nearly every form of disease of the skin. 
Some persons are so constituted that they can eat no kind 
of fish without experiencing unpleasant results. 

23. Vegetable Food. — The list of vegetable articles 
of diet is a very long one, including the grains from which 
our bread-stuffs are made, the vegetables from the garden, 
and the fruits. All the products of the vegetable king- 
dom are not alike useful. Some are positively hurtful; 
indeed, the most virulent poisons, as strychnia and prussic 
acid, are obtained from certain vegetables. Again, of such 

21 . What is " Trichina ?" How guarded against ? 

22. What part of fish is eaten? What does it resemble? Fish as food for 
digestion ? Fish as a diet ? 

23. List of vegetable articles? Usefulness of the different vegetables? 
Strychnia ? What further is said in relation to the nourishing and other qualities 
of vegetables ? 



72 FOOD AtfD DRLffK. 



articles as have been found good for food, some are more 
nourishing than others: some require very little prepara- 
tion for use, while others are hard and indigestible, and 
can only be used after undergoing many preparatory pro- 
cesses. Great care must therefore be exercised, and many 
experiments made, before we can arrive at a complete 
knowledge in reference to these articles of diet. Tea, 
coffee, and other substances from which drinks are made, 
ire of vegetable origin. ^ 

24. Bread. — Wheat is the principal and most valuable 
kind of grain for the service of man. Bread made from 
wheat-flour has been in use for many hundreds of years, 
and on this account, as well as because of its highly 
nourishing properties, has been aptly called " the staff of 
life." We never become tired of good bread as an article 
of daily food. 

The white kinds of flour contain more starch and less 
gluten than the darker, and are therefore less nutritious. 
The hard-grain wheat yields the best flour. Ir grinding 
wheat, the chaff or bran is separated by a process called 
" bolting." Unbolted flour is used for making brown or 
Graham bread. 

25. The form of bread most easily digested is that which 
has been " leavened," or rendered porous by the use of 
yeast, or by some similar method. Unleavened bread 
requires much more mastication. Hot bread is unwhole- 
some, because it is not firm enough to be thoroughly mas- 
ticated, but is converted into a pasty, heavy mass that is 
not easily digested. 

26. Wheaten bread contains nearly every principle requi- 
site for sustaining life, except fat. This is commonly added 
in other articles of diet, especially in butter, — " bread and 
butter," consequently, forming an almost perfect article of 

24. Wheat? "Staff of life?" White flour? Hard-grain wheats? Bolting? 
Graham oread ? 

25. Leavened bread ? Unleavened ? Hot bread ? 

26. Wheaten bread ? Bread and butter ? Experiment on the dog ? 



FOOD AND DRINK. 73 



food. The following experiment is recorded : " A dog 
eating ad libitum of white bread, made of pure wheat, and 
freely supplied with water, did not live beyond fifty days. 
He died at the end of that time with all the signs of 
gradual exhaustion." Death took place, not because there 
was anything hurtful in the bread, but because of the 
absence of one or more of the food-principles. 

27. The Potato. — The common or Irish potato is the 
vegetable most extensively used in this country and Great 
Britain. Among the poorer classes in Ireland it is the 
main article of food. While it is not so rich in nutritious 
substances as many others, it has some very useful qualities. 
It keeps well from season to season, and men do not weary 
of its continuous use. It is more than two-thirds water, 
the balance being chiefly starch, with a little albumen. 

28. The sweet potato differs from the white or common, 
in containing more water and a small proportion of sugar. 
The potato and the tomato belong to the same botanical 
order as the " nightshades," but do not possess their 
poisonous qualities, unless we except potatoes that are in 
the process of germination, when they are found injurious 
as food. 

29. Fruits. — These are produced, in this country, in 
great abundance, and are remarkable alike for their variety 
and delicious flavor ; consequently they are consumed in 
large quantities, especially during the warmer months. 
The moderate use of ripe fruits, in their season, is 
beneficial, because they offer a pleasant substitute for the 
more concentrated diet that is used in cold weather. The 
amount of solid nutriment they contain is, however, 
small. The percentage of water in cherries is seventy- 
five, in grapes eighty-one, in apples eighty two. Unripe 
fruits contain starch, which, during the process of ripening, 

27. State what is said of the Irish potato? 

28. Sweet potato ? Nightshades? Potatoes when germinating ? 

29. Fruits? Use of ripe fruit? Nutriment they contain? Starch in unripe 
fruits ? Cooking of unripe fruits ? 

4 



74 FOOD AtfD DRItfK. 

is converted into sugar. Such fruits are indigestible and 
should be avoided : cooking, however, in part removes the 
objections to them. 

30. Pure Water. — It is important that the water we 
drink and use in the preparation of food should be pure. 
It should be clear and colorless, with little or no taste or 
smell, and free from any great amount of foreign ingre- 
dients. Chemically pure water does not occur in nature : 
it is only obtained by the condensation of steam, carefully 
conducted, and is not as agreeable for drinking purposes 
as the water furnished by springs and streams. Kain-water 
is the purest occurring in nature ; but even this contains 
certain impurities, especially the portion which falls in the 
early part of a shower; for in its descent from the clouds, 
the particles floating in the air are caught by the falling 
drops. 

31. Water from springs and wells always contains more 
or less foreign matter of mineral origin. This imparts to 
the drink its pleasant taste — the sparkle, or "life," coming 
from the gases absorbed by the water during its passage 
under ground. The ordinary supply of cities is from some 
pure stream or pond conveyed from a distance through 
pipes, the limpid fluid containing generally only a small 
amount of impurity. 'Croton water, the supply of New 
York City, is very pure, and contains only four and a half 
grains to a gallon : the Ridgewood water of Brooklyn holds 
even less foreign matter. 

32. Drinking-water may contain as large a proportion as 
sixty to seventy grains per gallon of impurity, but a much 
larger quantity renders it unwholesome. The mineral 
spring waters, used popularly as medicines, are highly 
charged with mineral substances. Some of them, such as 



30. now should drinking-water be as regards color and smell? Chemically 
pure water ? How obtained ? A<;reeableness of perfectly pure water ? 

31. Spring and well water? Whence the sparkle or life? The water supply 
of cities ? Croton wate ? Ridgewood ? 

32. Impurities in drinking-water ? Mineral springs ? 



FOOD AND DRINK. 75 



the waters at Saratoga, contain three hundred grains and 
more to the gallon. 

33. Action of Water upon Lead. — The danger of 
using water that has been in contact with certain metals is 
well known. Lead is one of the most readily soluble, and 
probably the most poisonous of these substances in common 
use. When pure water and an untarnished surface of lead 
come m contact, the water gradually corrodes the metal, 
and soon holds an appreciable quantity of it in solution. 
When this takes place the water becomes highly injurious: 
the purer the water, and the more recent the use of the 
metal, the greater will be the danger. 

34. In cities, lead pipes are commonly used to convey 
water through the houses ; lead being also used in the con- 
struction of roofs, cisterns, and vessels for keeping water 
and other liquids. After the articles of lead have been in 
use several months, the danger of lead-poisoning dimin- 
ishes. An insoluble coating of the sulphate of lead forms 
upon the exposed surface, thus protecting it from further 
corrosion. It is, however, a wise precaution, at all times to 
reject the water or other fluid that has been in contact 
with leaden vessels over night, or for a number of hours. 
Allow the water in pipes to run freely before using. 

35. Coffee. — This is an important addition to diet, and 
if moderately used is beneficial to persons- of adult age. 
As commonly employed, it consists of an infusion in boil- 
ing water of the roasted and ground berry. The water 
extracts certain flavoring and coloring matters, but that 
which gives it its peculiar stimulant qualities is the alka- 
loid caffein. With most persons its action is that of a 
gentle stimulant, without any injurious reaction. It pro- 
duces a restful feeling after exhausting efforts of mind or 

33. What is stated of the action of water upon lead ? 

34. Lead in pipes and other things ? Advice ? What takes place after the arti- 
cles of lead have been used much ? What is wise ? 

35. Coffee as an article of diet? Of what does it consist? How does the 
water affect the coffee ? The peculiar stimulant ? How does it affect most per- 
sons? 



76 FOOD AND DRINK. 



body; it tranquilizes, but does not disqualify for labor; 
and hence it is highly esteemed by persons of literary pur- 
suits. 

36. Another property of coffee is, that it diminishes the 
waste of the tissues, and consequently permits the per- 
formance of excessive labor upon an economical and in- 
adequate diet. This has been tested among the miners of 
Belgium. Their allowance of solid food was below that 
found necessary in prisons and elsewhere; but, with the 
addition of about four pints of coffee daily, they were en- 
abled to undergo severe labor without reducing their mus- 
cular strength. The caravans which traverse the deserts 
are supported by coffee during long journeys and length- 
ened privation of food. Among armies it is indispensable 
in supplementing their imperfect rations, and in relieving 
the sense of fatigue after great exposure and long marches. 
When taken with meals, coffee is also thought to promote 
digestion. 

37. Tea. — The effects of tea-drinking are very similar 
to those of coffee, and are due to a peculiar principle called 
thein. This principle is probably the same as that found 
in coffee, caffein, since the chemical composition of both 
is precisely alike. Tea, as a beverage, is made from the 
dried leaves of the plant by the addition of hot water ; if 
the tea is boiled, the oil which gives it its agreeable flavor 
is driven off with the steam. There are two varieties of 
tea — the black and the green : the latter is sometimes in- 
jurious, producing wakefulness and other nervous symp- 
toms. The excessive use of either coffee or tea will cause 
wakefulness. 

38. During Dr. Kane's expedition in the Arctic regions, 
the effects of these articles were compared. "After re- 



The Caravans? 
Among armies ? Taken with meals ? 

37. Effects of tea-drinking? Peculiar principle? The tea beverage, how 
made ? Black and green tea ? Excessive use of tea or coffee ? 

38. Experiments made during Kane's expedition ? 



FOOD AND DRINK. 77 

peated trials, the men took most kindly to coffee in the 
morning and tea in the evening. The coffee seemed to 
continue its influence throughout the day, and they seemed 
to grow hungry less rapidly than after drinking tea, while 
tea soothed them after a day's hard labor, and the better 
enabled them to sleep. They both operated upon fatigued 
men like a charm, and their superiority over alcoholic 
stimulants was very decided." 

39. Chocolate is made from the seeds of the cocoa-tree, 
a native of tropical America. Its effects resemble some- 
what those of tea and coffee, but it is very rich in nutri- 
ment. Linnaeus, the botanist, was so fond of this beverage, 
that he gave to the cocoa-tree the name, Tlieohroma — " the 
Food of the Gods." Its active principle is theobromine 

40. Alcohol. — The list of beverages that are consumed 
for the sake of the alcohol they contain is a very long one. 
Their use is almost universally prevalent, every civilized 
nation, and nearly every barbarous one, having its favorite 
alcoholic drink ; and, as a general rule, the nations which 
stand the highest in civilization have the greatest varieties 
of these beverages, — at the same time using them the most 
intelligently and wisely. 

41. The wines and malt liquors that contain a small 
amount of alcohol are produced by fermentation. The 
beverages that hold a large proportion of alcohol, the 
"ardent spirits," are made by distillation. Enormous 
quantities of grains and fruits are thus yearly diverted 
from their proper uses as food ; some of these being corn, 
wheat, rye, barley, potatoes, and rice ; also the grape, apple, 
pear, peach, sugar-cane, cherry, fig, and orange. Wine, the 
fermented juice of the grape, has been in use from time 
immemorial, while the introduction of distilled liquors 
dates from a comparatively recent period. 

39. State what is said of chocolate. 

40. Use of alcoholic drinks, how general ? The rule given ? 

41 . The beverages produced by fermentation ? The ardent spirits ? Grains and 
fruits employed ? Long use of wine ? Of distilled liquors ? 



78 FOOD ASD DKiiSK. 



42. What is the physiological action of alcohol ? Its first 
and most evident action is stimulation : this effect is tran- 
sient, and is followed by a variable degree of depression. 
At first it sharpens the appetite and quickens digestion, 
but its habitual use impairs both. This stimulation is 
efficient in giving the system an artificial strength during 
some temporary derangement, and in enabling the endur- 
ance of unusual fatigue or exposure. The experience of 
Dr. Hayes, and other explorers of the polar regions, is that 
alcohol does not enable the body to resist the influence of 
cold, but, on the contrary, is always injurious. 

43. Another property it has in common with tea and 
coffee. It supports the powers of life, economizes food, and 
retards the waste of tissues ; in other words, it " banks the 
fires," and prevents their burning wastefully. On this 
principle we explain the restorative influence of wines or 
liquors during exhausting diseases, in convalescence, and 
after excessive labors of mind or body. 

44. Pure alcohol, or an excessive quantity of ardent 
spirits, is an undoubted poison, and has been frequently 
known to produce fatal results. Moderate amount of 
stimulants have been thought to increase strength, and in 
this view they have been called "alcoholic foods." This is 
not now conceded by scientific men. The prevailing opin- 
ion is, that they serve no useful purpose as an article of 
diet, and that their beneficial influence is limited to cases 
where the system is enfeebled, Avhere some unnatural de- 
mand is made upon the vital powers, or where the supply 
of food is insufficient. Hence, while alcohol has not the 
power to build up, it may obstruct the process of pulling 
down. 



42. Describe the action of alcohol upon the human system? Experience of 
Dr. Hayes and others ? 

43. Another property of alcohol ? How do we explain the restorative influen< 
of wines and liquors ? 

44. Alcohol, a poison? Moderate stimulants ? Prevailing opinion ? Hence 



. 



REVIEW QUESTIONS. 79 



QUESTIONS FOR TOPICAL REVIEW. 

PAGE 

1. How is the necessity for food shown ? 64 

2. To what process of waste and repair is the body constantly subjected ? 64 

3. How do you account for the sensations of hunger and thirst ? 05 

4. What further can you state having relation to the subject ? 65 

5. What can you state in regard to the quantity of food required for the 

support of life ? 65? 66 

6. What circumstances change the needs of persons, old and young, as re- 

gards food and drink ? 65 g? 

7. What becomes of all the food and drink we consume ? 66 

8. What further can you state in relation to the process of renovation through 

which the body passes ? 66 

9. What can you state of the habits of nations in respect to diet ? 66, 67, 69 

10. What in relation to the selection of articles for food ? 67 

11. What as respects the necessity for changing or varying the diet ? 67 

12. What has been proved as regards animal food ? 67 

13. Of what importance is milk as an article of food ? 67, 68 

14. What are the constituents of milk ? . . . 68 

15. What can you state of eggs as an article of food ? 68 

16. Of the meats, so called, as an article of food ? .' 68, 69 

17. What effect does cold have upon meats ? 69 

18. In what other way may beef and pork be preserved ? 69 

19. What can you state of salted meat as food, and of its continued use ? 69 

20. Whai change does meat undergo in the cooking ? 70, 71 

21. What directions are given for boiling meat ? 70 

22. What for roasting, and with what results ? 70, 71 

23. What is said about the frying of meats ? 71 

24. Give the statement in relation to trichina 71 

25. State what is said in relation to fish 71 

26. What is stated of the usefulness and other properties of the products of 

the vegetable kingdom ? 71, 72 

27. What further is said of vegetable food ? 71, 72 

28. Why is bread made of wheat flour so important as an article of food ? 72 

29. State whatever else you can in relation to bread 72, 73 

30. Give the statement respecting the potato 73 

31. What is stated of fruits, the use of them, their nutritious qualities, etc.? 73, 74 

32. How general is the existence of perfectly pure water ? 74 

33. What is stated in relation to drinking water ? 74, 75 

34. How does the action of water upon lead affect lead ? 75 

35. What further can you state on the subject ? ?5 

36. What properties has coffee as an article of diet ? 75. 76 

37. In what circumstances has coffee been found peculiarly beneficial ? 76 

38. What comparison is made between coffee, tea, and chocolate ? 76 

39. How are the wines, and malt and other alcoholic beverages produced ? 77 

40. What articles are employed in their production ? 77 

41. Describe the physiological action of alcohol 78 

42. What comparison is made between tea, coffee, and alcohol ? 78 

43. What can you state of alcohol, as a poison, a stimulant, and article of diet? 78 

44. What, then, can be said of alcohol as a recommendation ? 78 



80 DIGESTION. 



chapter vi. 
Digestion". 



The Principal Processes of Nutrition — The General Plan of Digestion 
— Mastication— Tlie Teeth — Preservation of the Teeth — Insalwation 
— The Stomach and the Gastric Juice — The Movements of the 
Stomach — Gastric Digestion — The Intestines — The Bile and Pan- 
creatic Juice — Intestinal Digestion — Absorption by means of Blood- 
vessels and Lacteals — The Lymphatic or Absorbent System — Tlie 
Lymph — Conditions which affect Digestion — The Quality, Quan- 
tity, and Temperature of the Food — The Influence of Exercise and 
Sleep. 

1. Nutrition. — The great design of food is to give 
nutriment ox nourishment to the body. But this is not 
accomplished directly, as the food must first pass through 
certain preparatory changes, as follows : (1), Digestion, by 
which the food is reduced to a soluble condition; (2), Ab- 
sorption, by which, when digested, it is imbibed into the 
blood; (3), Circulation, which carries the enriched blood 
to the various parts of the system; and (4), Assimilation r 
by which each tissue derives from the blood the materials 
necessary for its support. 

2. By these means the sustaining power of food is grad- 
ually developed and employed, and the vital machinery 
kept in working order, somewhat after the manner of the 
steam-engine. To operate the latter, the force imprisoned 
within the coal and water is set free and converted into 
motion by the combustion of the fuel and the vaporization 
of the water. It will be seen, however, when we come to 
study these operations in the human body, that they are 
conducted silently and harmoniously, with marvellous deli- 
cacy and completeness, and without that friction, and con- 

1 . Design of food ? How accomplished ? 

2. Sustaining power of food ? Simile of the engine ? Operation in the human 
body ? 



DIGESTION. 



81 



sequent loss of power, which attend the working of the 
most perfect machinery of man's invention. 

3. General Plan of Digestion. — The great change 
which food undergoes in digestion is essentially a reform- 
ing process, reducing articles of 
diet, which are at first more or 
less solid, crude, and coarse, to 
a liquid and finely comminuted 
condition, suitable for absorption 
into the blood. The entire pro- 
cess of digestion takes place in 
what is called the alimentary 
canal, a narrow, tortuous tube, 
about thirty feet in its entire 
length. This canal begins in 
the mouth, extends thence down- 
ward through the gullet to the 
stomach (a receptacle in which 
the principal work of digestion 
is performed), and thence onward 
through the small and large in- 
testines. 

4. The stomach and intestines 
are situated in the cavity of the 
abdomen (Fig. 16, C, and Fig. 22), FlG 16 ._ SECTrox OF THE TmINK 
and occupy about two-thirds of showing the cavities op the 

. . rr,, . . , . , . , Chest and Abdomen. 

its space. L he action to wh ich the Ai cavity of chest ; 
food is subjected in these organs ci Abdomen ? ; 
is of two kinds— mechanical and D ' E ' Spinal ,Column - 
chemical. By the former it is crushed, agitated, and car- 
ried onward from one point to another; by the latter it is 
changed in form through the solvent power of thy various 
:ive juices. 




3. Change of food in digestion ? Process of digestion? Describe ',(ae alimen- 
tary canal. 

4. Situation of the stomach and intestines ? Action of the food ? Mechanical 
action ? Chemical ? 

4* 



82 



DIGESTION. 



5. Mastication. — As soon as solid food is taken into 
the mouth, it undergoes mastication, or chewing. It is 
caught between the opposite surfaces of the teeth, and by 
them is cut and crushed into very small fragments. In 
the movements of chewing, 
the lower jaw plays the chief 
part; the upper jaw, having 
almost no motion, acts sim- 
ply as a point of resistance, 
to meet the action of the 
former. These movements 
of the lower jaw are of three 
sorts: a vertical or cutting, 
a lateral or grinding, and a 
to-and-fro or gnawing mo- 
tion. 

6. The teeth are composed 
of a bone-like material, and 
are held in place by roots 
running deeply into the jaw. 
The exposed portion, or 
"crown," is protected by a 
thin layer of enamel (Fig. 
17, a), the hardest substance 




Fig. 17.— Section of a Tooth. 

a, Enamel; b, Cavity; cc, Eoots ; 

d, Body of the Tooth. 



in the body, and, like flint, is capable of striking fire with 
steel. In the interior of each tooth is a cavity, containing 
blood-vessels and a nerve, which enter it through a minute 
opening at the point of the root (Fig. 19). 

7. There are two sets of teeth ; first, those belonging to 
the earlier years of childhood, called the milk teeth, which 
are twenty in number and small. At six or eight years of 
age, when the jaw expands, and when the growing body 
requires a more powerful and numerous set, the roots of 



5. Describe the process of mastication ? How many and what movements ? 

6. Composition of the teeth? Enamel of the teeth ? Interior of teeth ? 

7. The milk teeth ? The permanent teeth? 



DIGESTION. 



83 



the milk teetli are absorbed, and the latter are "shed," or 
fall out, one after another (Fig. 18), to make room for the 
permanent set. 




Fig. 18.— Section op the Jaws. 
1' 2' 3' 4 5', The Milk Teeth ; 1" to 8", The Germs of the Permanent Set. 

8. There are thirty-two teeth in the permanent set, as 
many being in one jaw as the other. Each half-jaw has 
eight teeth, similarly shaped and arranged in the same 
order : thus, two incisors, one canine, two bicuspids, and 
three molars. The front teeth are small, sharp, and chisel- 
edged, and are well adapted for cutting purposes; hence 
their name incisors. The canines stand next, one on each 
side of the jaw; these receive their name from their resem- 
blance to the long, pointed tusks of the dog (Fig. 19). 



8,9. Numher of teeth ? How distributed ? 



84: 



DIGESTION. 



9. The bicuspids, next in order, are larger and have a 
broader crown than the former; while behind them are 
the molars, the largest and most powerful of the entire set. 
These large back teeth, or "grinders," present a broad, 
rough surface, suitable for holding and crushing the food. 




Fig. 19.— Section of the Jaws— Right Side. 
V, A, N, Veins, Arteries, and Nerves of the Teeth, The root of one tooth in each 
jaw is cut vertically to show the cavity and the blood-vessels, etc., within it. 
1 to 8, Permanent Teeth. 

The third molar, or " wisdom tooth," is the last to be cut, 
and does not appear until about the twenty-first year. 






DIGESTION. 85 



The order of arrangement of the teeth is indicated by the 
following dental formula: — 

M 3 M 

B"" ^B 
A 

0' 4 x O 
I 



10. It is interesting, at this point, to notice the different 
forms of teeth in different animals, and observe how ad- 
mirably their teeth are suited to the respective kinds of 
food upon which they subsist. In the carnivora, or flesh- 
feeders, the teeth are sharp and pointed, enabling them 
both to seize their prey, and tear it in pieces ; while the 
herUvora, or vegetable-feeders, have broad, blunt teeth, 
with rough crowns, suitable for grinding the tough grasses 
and grains upon which they feed. Human teeth partake 
of both forms ; some of them are sharp, and others are 
blunt ; they are therefore well adapted for the mastication, 
of both flesh and vegetables. Hence we argue that, 
although man may live exclusively upon either vegetable 
or animal food, he should, when possible, choose a diet 
made up of both varieties. 

11. Preservation of the Teeth. — In order that the 
teeth shall remain in a sound and serviceable condition, 
some care is of course requisite. In the first place, they 
require frequent cleansing; for every time we take food, 
some particles of it remain in the mouth ; and these, on 
account of the heat and moisture present, soon begin to 
putrefy. This not only renders the breath very offensive, 
but promotes decay of the teeth. 

1 0. Different forms of teeth ? Human teeth ? The inference ? 

1 1 . Cleaning of teeth ? Effects of not cleaning ? 



86 DIGESTION - . 



12. The saliva, or moisture of the mouth, undergoes a 
putrefactive change, and becomes the fertile soil in which 
a certain minute fungus has its growth. This fluid, too, if 
allowed to dry in the mouth, collects upon the teeth in the 
form of an unsightly, yellow concretion, called tartar. 
To prevent this formation, and to remove other offensive 
substances, the teeth should be frequently cleaned with 
water, applied by means of a soft tooth-brush. The de- 
struction of the tartar fungus is best effected by the use 
of a weak solution of carbolic acid. 

13. Again, it should be borne in mind that the enamel, 
Nature's protection for the teeth, when once destroyed, is 
not formed anew ; and the body of the tooth thus exposed, 
is liable to rapid decay. On this account, certain articles 
are to be guarded against ; such as sharply acid substances 
that corrode the enamel, and hard substances that break 
or scratch it — as gritty tooth powders, metal tooth picks, 
and the shells of hard nuts. Sudden alternations from 
heat to cold, when eating or drinking, also tend to crack 
the enamel. 

14. Insalivation. — When the morsel of food is cut and 
ground by the teeth, it is at the same time also intimately 
mixed with the saliva, or fluids of the mouth. This con- 
stitutes the second step of digestion, and is called insaliva- 
tion. The saliva, the first of the digestive solvents, is a 
colorless, watery, and frothy fluid. It is secreted (i. e. 
separated from the blood) partly by the mucous mem- 
brane which lines the mouth ; but chiefly by the salivary 
glands, of which there are three pairs situated near the 
mouth. 

15. These glands consist of clusters of very small 



12. Effects upon the saliva? Formation of tartar? How prevented? How 
destroyed ? 

13. Detraction of the enamel ? How sruarded against? 

1 4. Mixing of food with the saliva ? What is the saliva ? How secreted ? The 
salivary glands ? 

15. The flow of saliva ? The thought of food ? Anxiety and grief? Animals 
fed upon dry and coarse food ? 



DIGESTION. 



87 




pouches, around which a delicate network of blood-vessels 
is arranged: they empty into the mouth by means of 
little tubes, or 
ducts. The flow 
from these glands 
is at all times suf- 
ficient to maintain 
a soft and moist 
condition of the 
tongue and mouth; 
but when they are 
excited by the pres- 
ence and taste of 
food, they pour 

forth the Saliva ^io. 20— Structure of a Salivary Gland. 

more freely. Even the mere thought of food will at 
times cause the saliva to flow, as when the appetite is 
stimulated by the sight or smell of some savory article ; so 
that the common expres- 
sion is correct that " the 
mouth waters" for the fa- 
vorite articles of food. 
Anxiety and grief prevent 
its flow, and cause "the 
tongue to cleave to the 
roof of the mouth." In 
the horse and other ani- 
mals, that feed upon dry 
and coarse fodder, and re- 
quire an abundant sup- 
ply of saliva, we find large 
salivary glands, as well as powerful muscles of mastication. 
16. The mingling of the saliva with the food seems a 
simple process, but it is one that plays an important part 




Fig. 21.— The Head of a Horse, showing the 
large salivary gland (a), its duct (6), the 
muscles of mastication (c, d, e,f, and g). 



1 6. Importance of the process ? The first place ? The second ? The third ? 



DIGESTION. 



in digestion. In the first place, it facilitates the motions 
of mastication, by moistening the food and lubricating the 
various organs of the mouth. Secondly, it prepares the 
way for other digestive acts : by the action of the teeth, 
the saliva is forced into the solid food, softens the harder 
substances, and assists in converting the whole morsel into 
a semi-solid, pulpy mass, that can be easily swallowed, and 
readily permeated by other digestive fluids. The saliva 
also, by dissolving certain substances, as sugar and salt, 
develops the peculiar taste of each ; whereas, if the tongue 
be dry and coated, they are tasteless. Hence, if substances 
are insoluble, they are devoid of taste. 

17. Finally, the saliva has the property of acting chemi- 
cally upon the food. As we have before stated (Chap. IV.), 
starch, as starch, cannot enter the tissues of the body ; but, 
in order to become nutriment, must first be changed to 
grape sugar. This change is, in part, effected by the saliva, 
and takes place almost instantly, whenever it comes in con- 
tact with cooked starch. This important function is due 
to an organic ingredient of the saliva called ptyalin. 
This substance has been extracted from the saliva by 
the chemist, and has been found, by experiment, to 
convert into sugar two thousand times its own weight of 
starch. 

18. Importance of Mastication and Insaliva- 
tion. — Each of these processes complements the other, 
and makes the entire work available; for, by their joint 
action, they prepare the food in the best possible manner 
for further digestive changes. The knowledge of these 
preliminary functions will appear the more important, 
when we reflect that they are the only ones which we can 
regulate by the will. For, as soon as the act of swallowing 
begins, the food not only passes out of sight, but beyond 



17. Its final importance ? Starch ? How effected ? Ptyalind ? 

1 8 . Each of the processes ? Why is a knowledge of the digestive functions 
important? '"How shown? 



DIGESTION. 89 

control ; and the subsequent acts of digestion are conse- 
quently involuntary and unconsciously performed. 

19. It is generally known that rapid eating interferes 
with digestion. How does this occur ? In the first place, 
in rapid eating, the flow of the saliva is insufficient to 
moisten the solid parts of the food, so that they remain too 
hard and dry to be easily swallowed. This leads to the 
free and frequent use of water, or some other beverage, at 
meals, to "wash down" the food, — a most pernicious prac- 
tice. For these fluids, not only cannot take the place of 
the natural digestive juices, but, on the contrary, dilute 
and weaken them. 

20. Secondly, the saliva being largely the medium of the 
sense of taste, the natural flavors of the food are not devel- 
oped, and consequently it appears comparatively insipid. 
Hence the desire for high-seasoned food, and pungent 
sauces, that both deprave the taste and over excite the 
digestive organs. Rapid eating also permits the entrance 
of injurious substances which may escape detection by the 
taste, and be unconsciously received into the system. In 
some instances, the most acrid and poisonous substances 
have frequently been swallowed " by mistake," before the 
sense of taste could act, and demand their rejection. 

21. Thirdly, the food, being imperfectly broken up by 
the teeth, is hurried onward to the stomach, to be by it 
more thoroughly divided. But the task thus imposed upon 
the stomach, it is not at all adapted to perform ; so that the 
crude masses of food remain a heavy burden within the 
stomach, and a source of distress to that organ, retarding 
the performance of its legitimate duty. Hence persons 
who habitually eat too rapidly, frequently fall victims to 
dyspepsia. Rapid eating also conduces to overeating. 
The food is introduced so rapidly, that the system has not 

19. Rapid eating? Describe the process and effects. 

20. Loss of taste? Another effect of rapid eating? Mistakes? 

2 1 . Effect of imperfectly broken food in the stomach ? Dyspepsia ? Over- 
eating ? 



90 



DIGESTION. 



time to recognize that its real wants are met, and that its 
losses have been made good; and hence the appetite con- 
tinues, although more nutriment has been swallowed than 
the system requires, or can healthfully appropriate. 

22. The Stomach. — As soon as each separate portion 
of food is masticated and insalivated, it is swallowed; that 

is, it is propelled down- 
ward to the stomach, 
through a narrow mus- 
cular tube about nine 
inches in length, called 
the oesophagus, or gul- 
let (Fig. 23). The 
stomach is the only 
large expansion of the 
digestive canal, and is 
the most important or- 
gan of digestion. It is 
a hollow, pear-shaped 
pouch, having a ca- 
pacity of three pints, 
in the adult. Its walls 
are thin and yielding, 
and may become un- 
naturally distended, as 
in the case of those 
who subsist on a bul- 
ky, innutritious diet, 
and of those who habitually gormandize. 

23. The stomach has also two openings; that by which 
food enters, being situated near the heart, is called the 
cardiac, or heart orifice; the other is the pylorus, or 
"gatekeeper," which guards the entrance to the intestines, 




Pig. 22.— Section of Chest and Abdomen. 

A, Heart. D, The Liver. 

B, The Lungs. E, Large Intestine. 

C, Stomach. G, Small Intestine. 



22. Gullet? Describe the stomach and. its location. Effects of gormandizing? 

23. Heart-orifice? Gatekeeper? Coins, etc.? Indication of the goft and 
yielding texture of the stomach ? 



DIGESTION. 



91 



and, under ordinary circumstances, permits only such 

matters to pass it as have first been properly acted upon 

in the stomach. Coins, buttons, and the like are, however, 

readily allowed to pass, because they can be of no use if 

retained. The soft and 

yielding texture of this 

organ — the stomach — 

indicates that it is not 

designed to crush and 

comminute solid articles 

of food, y 

24. The Gastric 6 — 
Juice. — We have seen 
how the presence of food 
in the mouth excites the 
salivary glands, causing 
the saliva quickly to 
flow. In the same man- 
ner, when food reaches 
the stomach, its inner 
lining, the mucous mem- 
brane, is at once excited 
to activity. At first its 
surface, which while the 
stomach is empty pre- 
sents a pale pink hue, 
turns to a bright red 
color, for the minute 
blood-vessels which 
course through it, are filled with blood. Presently a clear, 
colorless, and acid fluid exudes, drop by drop, from its nu- 
merous minute glands or "tubules," until finally the surface 
is moistened in every part, and the fluid begins to mingle 
with the food. This fluid is termed the gastric juice. 




Fig. 23.— The Organs of Digestion. 

O, Oesophagus. I, Small Intestines. 
S, Stomach. C, Large Intestines. 

L, Liver. P, Pancreas. 

M, Pylorus. N, Spleen. 

G, Gall-bladder. 



24. What is meant by the gastric juice ? 



92 DIGESTION. 



25. The gastric juice is the proper solvent of certain 
articles of food, especially those belonging to the albu- 
minoid class. This solvent power is due to its peculiar in- 
gredient, pepsin; in digestion, this substance acts like a 
ferment ; that is, it induces changes in the food simply by 
its presence, but does not itself undergo change. The acid- 
ity of the gastric juice, which is due to lactic acid, is not 
accidental; for we find that the pepsin cannot act in an 
alkaline solution — that is, one which is not acid or neutral. 
The quantity of gastric juice secreted daily is very large, 
probably not less than three or four pints at each meaL 
Though this fluid is at once used in the reduction of the 
food, it is not lost; since it is soon re-absorbed by the 
stomach, together with those parts of the food which it 
has digested and holds in solution. 

26. Movements of the Stomach. — The inner coat- 
ing of the stomach is the mucous membrane, which, as we 
have seen, furnishes the gastric juice. Next to this coating 
lies another, called the muscular coat, composed of invol- 
untary muscular fibres, some of which run circularly, and 
others in a longitudinal direction. These expand to ac- 
commodate the food as it is introduced, and contract as it 
passes out. In addition, these fibres are in continual mo- 
tion while food remains in the stomach, and they act in 
such manner that the contents are gently turned roun 
from side to side, or from one end of it to the other. 

27. By these incessant movements of the stomach, 
called the peristaltic movements, the gastric juice comes 
in contact with all parts of the food. We are, however, 
not conscious that these movements take place, nor have 
we the power to control them. When such portions of the 
food as are sufficiently digested approach the pylorus, it 



25. What is the office of the gastric juice? Acidity of the gastric juice? 
Quantity of gastric juice used ? What becomes of it ? 

26. Muscular coat of the stomach? Expansion and contraction of its fibres? 
Action of the fibres ? 

27. Peristaltic movements? What is said of our consciousness of and power 
over these movements ? Describe the movements of the pylorus. 



DIGESTION. 93 



expands to allow them to pass out, and it closes again to 
confine the residue for further preparation. 

28. The knowledge of these and other interesting and 
instructive facts has been obtained by actual observation ; 
the workings of the stomach of a living human being have 
been laid open to view and examined — the result of a re- 
markable accident. Alexis St. Martin, a Canadian voyageur, 
received a gun-shot wound which laid open his stomach, 
and which, in healing, left a permanent orifice nearly an 
inch in diameter. Through this opening the observer 
could watch the progress of digestion, and experiment with 
different articles of food. Since that occurrence, artificial 
openings into the stomach of the inferior animals have 
been repeatedly made, so that the facts of stomach-digestion 
are very well ascertained and verified. 

29. Gastric Digestion. — What portions of the food 
are digested in the stomach ? It was formerly thought 
that all the great changes of digestion were wrought here, 
but later investigation has taught us better. We now know 
that the first change in digestion takes place in the mouth, in 
the partial conversion of starch into sugar. We also know 
that, of the three organic food principles (considered in 
Chapter III.) two — the fats and the sugars — are but slightly 
affected by the stomach ; but that its action is confined to 
that third and very important class, from which the tissues 
are renewed, the albuminoids. A few articles need no 
preparation before entering the system, as water, salt, and 
grape-sugar. These are rapidly taken up by the blood- 
vessels of the stomach, which everywhere underlie its 
mucous membrane in an intricate and most delicate net- 
work. In this way the function of absorption begins. 

30. The albuminoid substances are speedily attacked and 



28. How has the knowledge and the workings of the stomach been ascertained r 
St. Martin? How else? 

29. What was formerly thought ? What do we now know ? What else do we 
now know ? Water, ealt, and sugar ? Absorption ? 

30. Albuminose? The process ? Chyme? 



94 DIGESTION. 

digested by the gastric juice. From whatever source they 
are derived, vegetable or animal, they are all transformed 
into the same digestive product, culled albuminose. This is 
very soluble in water, and is readily absorbed by the blood- 
vessels of the stomach. After a longer or shorter time, 
varying from one to five hours, according to the individual 
and the quantity and quality of his food, the stomach will 
be found empty. Not only has the digested food passed 
out, but also those substances which the stomach could 
not digest or absorb have passed little by little through 
the pylorus, to undergo further action in the intestines. 
At the time of its exit, the digested food is of a pulpy 
consistence, and dark color, and is then known as the chyme. 

31. The Intestines. — The intestines, or "bowels," 
are continuous with the stomach, and consist of a fleshy 
tube, or canal, twenty-five feet in length. The small 
intestine, whose diameter is about one inch and a half, is 
twenty feet long and very tortuous. The large intestine is 
much wider than the former, and five feet long (Fig. 23). 
The general structure of these organs resembles that of the 
stomach. Like it, they are provided with a mucous mem- 
brane, or inner lining, whence flow their digestive juices; 
and, just outside of this, a muscular coat, which propels 
the food onward from one point to another. 

32. Moreover, both the intestines and stomach are envel- 
oped in the folds of the same outer tunic or membrane, called 
the peritoneum. This is so smooth and so well lubricated, 
that the intestines have the utmost freedom of motion. 
In the small intestines, the work of digestion is completed, 
the large intestine receiving from them the indigestible 
residue of the food, and in time expelling it from the body. 

33. Intestinal Digestion. — As soon as the food 
passes the pylorus and begins to accumulate in the upper 

3 1 . What are the intestines ? The small intestines ? The large intestines f 
Their structure ? 

32. Peritoneum ? The work of digestion ? 

33. The presence of food in the intestines ? Bile ? 



DIGESTION". 95 

part of the intestines, it excites the flow of a new digestive 
fluid, which enters through a small tube, or duct, about 
three inches below the stomach. It is formed by the union 
of two distinct fluids — the bile and the iiancreatic juice. 
The bile is secreted by the liver, which is the largest gland 
of the body, and is situated on the right side and upper 
part of the abdomen (Fig. 22). The bile is constantly 
formed, but it flows most rapidly during digestion. Dur- 
ing the intervals of digestion it is stored in the gall-bladder, 
a small membranous bag attached to the under side of the 
liver. This fluid is of a greenish-yellow color, having a 
peculiar smell, and a very bitter taste. 

34. The pancreatic juice is the product of a gland called 
'jaz pancreas, situated behind the stomach. This fluid is col- 
orless, viscid, and without odor. Like the digestive juices 
previously described, it owes its solvent power to its pecu- 
liar ferment principle, called pancreatin. By the joint 
action of these fluids, the fatty parts of the food are pre- 
pared for absorption. By previous steps of digestion the 
fats are merely separated from the other components of the 
food ; but here, within the intestines, they are reduced to a 
state of minute division, or emulsion, resembling the con- 
dition of butter in milk, before it has been churned. 
There results from this action a white and milky fluid, 
termed the chyle, which holds in solution the digestible 
portions of the food, and is spread over the extensive 
absorbent surface of the small intestines. 

35. The mucous membrane of the intestines, also, 
secretes or produces, a digestive fluid by means of numer- 
ous "follicles," or minute glands; this is called the in- 
testinal juice. From experiments on the inferior animals, 
it has been ascertained that this fluid exerts a solvent influ- 
ence over each of the three organic food principles, and in 
this way may supplement and complete the action of the 

34. The pancreatic juice ? The joint action of these fluids ? 

35. The mucous membrane ? Experiments on inferior animals ? 



96 DIGESTION. 



fluids previously mentioned, viz. : — of the saliva in convert- 
ing starch into sugar, of the gastric juice in digesting the 
albuminoids, and of the pancreatic juice and bile in 
emulsifying the fats. 

36. Absorption. — With the elaboration of the chyle, 
the work of digestion is completed ; but, in a certain sense, 
the food is yet outside of the body ; that is, the blood is not 
yet enriched by it, and it is not in a position to nourish the 
tissues. The process by which the liquefied food passes out 
of the alimentary canal into the blood is called absorption. 
This is accomplished in two ways ; first, by the blood-vessels. 
We have seen how the inner membrane of the stomach is 
underlaid by a tracery of minute and numerous vessels, 
and how some portions of the food are by them absorbed. 
The supply of blood-vessels to the intestines is even 
greater; particularly to the small intestines, where the 
work of absorption is more actively carried on. 

37. The absorbing surface of the small intestines, if con- 
sidered as a plane surface, amounts to not less than half a 
square yard. Besides, the mucous membrane is formed in 
folds with an immense number of thread-like prolongations, 
called villi, which indefinitely multiply its absorbing capa- 
city. These minute processes, the villi, give the surface 
the appearance and smoothness of velvet; and during 
digestion, they dip into the canal, and, by means of their 
blood-vessels, absorb its fluid contents, just as the sjiongi- 
oles which terminate the rootlets of plants, imbibe moisture 
from the surrounding soil. 

38. Secondly, absorption is also effected by the lacteals, a 
set of vessels peculiar to the small intestines. These have 
their beginnings in the little villi just mentioned, side by 
side with the blood-vessels. These two sets of absorbents 
run in different courses, but their destination is the same, 

36, 37. How much thus far has been done with the food ? The next process ? 
Give the first way. 

38. How is absorption effected in another way? Describe it. Name of the 
lacteals ? Thoracic duct ? 



DIGESTION. 



97 



which is the right side of the heart. The lacteals receive 
their name from their milky-white appearance. After a 
meal containing a por- 
tion of fat, they are 
then distended with 
chyle, which they are 
specially adapted to 
receive : at other times 
they are hardly dis- 
cernible. The lacteals 
all unite to form one 
tube, the thoracic duct, 
which passes upward 
through the thorax, or 
chest, and empties into 
a large vein, situated 
just beneath the left 
collar-bone. 

39. The Absorb- 
ents. — The lacteals 
belong to a class of 
vessels known as absorbents, or lymphatics, which ram- 
ify in nearly all parts of the body, except the brain and 
spinal cord. The fluid which circulates through the lym- 
phatics of the limbs, and all the organs not concerned in 
digestion, is called lymph. This fluid is clear and color- 
less, like water, and thus differs from the milky chyle 
which the lacteals carry after digestion : it consists chiefly 
of the watery part of the blood, which was not required by 
the tissues, and is returned to the blood by the absorbents 
or lymphatics. 

40. Circumstances affecting Digestion. — What 
length of time is required for the digestion of food ? From 
observations made, in the case of St. Martin, the Canadian 




Fig. 24.— The Lacteals. 
A, Small Intestine. B, Lacteals. 
C, Thoracic Duct. D, Absorbents. 

E, Blood-vessel. 



39. The absorbents ? Lymph ? What farther of the lymph ? 

40. What can you state as to the time required for digestion? 



98 DIGESTION. 



already referred to, it has been ascertained that, at the end 
of two hours after a meal, the stomach is ordinarily empty. 
How much time is needed to complete the digestion of 
food, within the small intestines, is not certain ; but, from 
what we have learned respecting their functions, it must 
be evident that it largely depends upon the amount of 
starch and fat which the food contains. 

41. In addition to the preparations which the food 
undergoes in cooking, which we have already considered, 
many circumstances affect the duration of digestion ; such 
as the quality, quantity, and temperature of the food ; the 
condition of the mind and body ; sleep, exercise, and habit. 
Fresh food, except new bread and the flesh of animals 
recently slain, is more rapidly digested than that which is 
stale ; and animal food more rapidly than that from the 
vegetable kingdom. 

42. Food should not be taken in too concentrated a form, 
the action of the stomach being favored when it is some- 
what bulky ; but a large quantity in the stomach often re- 
tards digestion. If the white of one egg be given to a dog, 
it will be digested in an hour, but if the white of eight 
eggs be given it will not disappear in four hours. A wine- 
glassful of ice-water causes the temperature of the stomach 
to fall thirty degrees ; and it requires a half-hour before it 
will recover its natural warmth — about a hundred degrees — 
at which the operations of digestion are best conducted. 
A variety of articles, if not too large in amount, is more 
easily disposed of than a meal made of a single article; 
although a single indigestible article may interfere with 
the reduction of articles that are easily digested. 

43. Strong emotion, whether of excitement or depression, 
checks digestion, as do also a bad temper, anxiety, long 
fasting, and bodily fatigue. The majority of these condi- 



41. Circumstances affectine duration of digestion ? Fresh food ? 

42. Food in concentrated form ? A large quantity of food? Experiment on 
the dog ? Ice-water ? Variety of articles ? 

43. Strong emotion ? The tongue of the patient ? 



DIGESTION. 99 

tions make the mouth dry, that is, they restrain the flow 
of the saliva ; and without doubt they render the stomach 
dry also, by preventing the flow of the gastric juice. And, 
as a general rule, we may decide, from a parched and coated 
tongue, that the condition of the stomach is not very dis- 
similar, and that it is unfit for the performance of digestive 
labor. This is one of the points which the physician bears 
in mind when he examines the tongue of his patient. 

44. The practice of eating at short intervals, or " between 
meals," as it is called, has its disadvantage, as well as rapid 
eating and over-eating, since it robs the stomach of its needed 
period of entire rest, and thus overtasks its power. With 
the exception of infants and the sick, no persons require 
food more frequently than once in four hours. Severe 
exercise either directly before or directly after eating retards 
digestion ; a period of repose is most favorable to the proper 
action of the stomach. The natural inclination to rest 
after a hearty meal may be indulged, but should not be 
carried to the extent of sleeping ; since in that state the 
stomach, as well as the other parts of the body, seeks 
release from labor. 

44. Eating between meals ? Severe exercise ? Sleep after meals ? 



100 REVIEW QUESTIONS. 



QUESTIONS FOR TOPICAL REVIEW. 

PAGE 

1. What do you understand by nutrition ? 80 

2. How is the process of nutrition carried on ? 80 

3. What further can you state on the subject ? 80, 81 

4. Describe the general plan of digestion 81 

5. How is the process of mastication carried on ? 80, S2 

6. State what you can in relation to the formation of the teeth 82, 86 

7. What, in relation to their arrangement ? 83, 84 

8. What, in relation to the process of " shedding ?" 82, 83, 84 

9. In relation to the different forms of teeth in different animals ? 85 

10. What causes operate to injure or destroy the teeth ? 85, 86 

11. What suggestions and directions are given for the preservation of the 

teeth ? 85, 86 

12. What do you understand by insalivation ? 80, 86 

13. How is the process of insalivation carried on ? 86, 8T, 88 

14. Of what importance is the saliva to the process ? 87, 88 

15. Of what importance are mastication and insalivation ? 88, 89 

16. Describe the consequences of rapid eating 89, 90 

17. What becomes of the food directly after it has undergone mastication 

and insalivation ? 90 

18. Describe the location and formation of the stomach 90, 91, 92 

19. Describe the process by which the gastric juice is formed 91 

20. What are the properties and uses of the gastric juice ? 92 

21. What are the movements of the stomach, and what their uses ? 92, 93 

22. What further can you state on the subject ? 93 

23. What portions of the food are digested in the stomach ? 93, 94 

24. What are the first changes of digestion ? 93 

25. Describe the location and formation of the stomach 94 

26. What further can you state in relation to the stomach ? 94 

27. Describe the process of intestinal digestion 94, 95, 96 

28. What do you understand by absorption ? 80, 96 

29. How is the process of absorption effected ? 96, 97 

30. What are the lacteals, and of what use are they ? 96, 97 

31. What length of time is required for the digestion of food ? 97, 98 

32. What circumstances, of food, affect digestion ? 98 

33. What circumstances, of emotion, affect digestion ? 98, 99 

34. What suggestions and directions are given upon the subject of eating 

and drinking ? 98, 99 





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CIRCULATION OF THE BLOOD. 
( Heart .Lungs, Arl erie s & V*' ins.] 



THE CIRCULATION lUl 



chapter vii. 

The Circulatiok. 

The Blood— Its Plasma and Corpuscles— Coagulation of the Blood— The 
Uses of the Blood— Transfusion— Change of Color— The Organs of 
the Circulation— The Heart, Arteries, and Veins— T7ie Cavities 
and Valves of the Heart— Its Vital Energy— Passage of the Blood 
through the Heart— The Frequency and Activity of its Movements — 
The Pulse— The Spygmograph—T7ie Capillary Blood-vessels— The 
Bate of the Circulation— Assimilation— Injuries to the Blood-vessels. 

1. The Blood. — Every living organism of the higher 
sort, whether animal or vegetable, requires for the main- 
tenance of life and activity, a circulatory fluid, by which 
nutriment is distributed to all its parts. In plants, this 
fluid is the sap; in insects, it is a watery and colorless 
blood; in reptiles and fishes, it is red but cold blood; 
while in the nobler animals and man, it is the red and 
warm blood. 

2. The blood is the most important, as it is the most 
abundant, fluid of the body; and upon its presence, under 
certain definite conditions, life depends. On this account 
it is frequently, and very properly, termed "the vital 
fluid." The importance of the blood, as essential to life, 
was recognized in the earliest writings. In the narration 
of the death of the murdered Abel, it is written, " the voice 
of his Mood crieth from the ground." In the Mosaic law, 
proclaimed over thirty centuries ago, the Israelites were 
forbidden to eat food that contained blood, for the reason 
that "the life of the flesh is in the blood." With the 
exception of a few tissues, such as the hair, the nails, 
and the cornea of the eye, blood everywhere pervades the 
body, as may be proven by puncturing any part with a 

1 . What is required by every living organism ? In plants ? Insects ? Reptiles ? 
Man? 

2. Importance and abundance of blood? Dependence of life ? Abel ? Mosaic 
law ? In what part of the body is blood not found ? Quantity of blood in the body ? 



102 



THE CIRCULATION. 



needle. The total quantity of blood in the body is esti- 
mated at about one-eighth of its weight, or eighteen 
pounds. 

3. The color of the blood, in man and the higher ani- 
mals, as is well known, is red ; but it varies from a bright 
scarlet to a dark purple, according to the part whence it is 
taken. " Blood is thicker than water," as the adage truly 
states, and has a glutinous quality. It has a faint odor, 
resembling the peculiar odor of the animal from which it 
is taken. 

4. When examined under the microscope, the blood no 
longer appears a simple fluid, and its color is no longer red. 
It is then seen to be made up of two distinct parts: first, 
a clear, colorless fluid, called the plasma ; and secondly, 
of a multitude of minute solid bodies, or corpuscles, 
that float in the watery plasma. The plasma, or nutritive 
liquid, is composed of water richly charged with materials 
derived from the food, viz., ' albumen, which gives it 
smoothness and swift motion ; fibrin ; certain fats ; traces 
of sugar ; and various salts. 

5. The Blood Corpus- 
cles. — In man, these remark- 
able "little bodies," as the 
word corpuscles signifies, are 
of a yellow color, but by their 
vast numbers impart a red 
hue to the blood. They are 
very small, having a diameter 
of about -j^Vo °f an mcn ? an( l 
being one-fourth of that frac- 
tion in thickness; so that if 

Fig. 25.— The Blood Corpuscles. . _ , n . 

3,500 of them were placed in 
line, side by side, they would only extend one inch; or, if 




3. Color of blood? Its consistence ? Odor? 

4. What is stated of the blood as viewed under the microscope ? 

5. State what you can of the little bodies called corpuscles. 



THE CIRCULATION 



103 



*@- 



piled one -above another, it would take at least 14,000 of 
them to stand an inch high. Although so small in size, 
they are very regular in form. As seen under the micro- 
scope, they are not globular or spherical, but flat, circular, 
and disc-like, with central depressions on each side, some- 
what like a pearl button that has not been perforated. In 
freshly-drawn blood they show a disposition to arrange 
themselves in little rolls like coins (Fig. 25). 

6. The size and shape of the blood corpuscles vary in 
different animals, so that it is possible to discriminate be- 
tween those of man and the lower 
animals (Fig. 26). This is a point of 
considerable practical importance. 
For example, it is sometimes desir- 
able to decide in a court of justice 
the source, whether from man or an 
inferior animal, of blood stains upon 
the clothing of an accused person, or 
upon some deadly weapon. This may 
be done by a microscopical examina- 
tion of a minute portion of the dried 
stain, previously refreshed by means 
of gum-water. Certain celebrated 
cases are recorded in which the guilt 
of criminals has been established, and 
they have been condemned and pun- 




Fig. 26. 



a, Oval Corpusclesof a fowL 

ished upon the evidence which sci- * gSKft s Ck frog ' 
ence rendered on this single point, ^f^Tl^Vt 
the detecting of the human from Rifled 4oo m 5mes. rpuscles 
other blood. 

7. The character of the blood of dead, extinct, and even 
fossil animals, such as the mastodon, has been ascertained 
by obtaining and examining traces of it which had been 
shut up, perhaps for ages, in the circulatory canals of bone. 
A means of detecting blood in minute quantities is found 



6. The size and sbape of the corpuscles ? Why is the fact important ? 

7. The character of the blood of dead animals ? Means of detecting such blood ? 



104 THE CIRCULATION. 

in the spectroscope, the same instrument by which the 
constitution of the heavenly bodies has been studied. If 
a solution containing not more than one-thousandth part 
of a grain of the coloring matter of the corpuscle, be ex- 
amined, this instrument will detect it. 

8. The corpuscles, just described, are known as the red 
blood corpuscles. Besides these, and floating along in the 
same plasma, are the white corpuscles. These are fewer 
in number, but larger and globular in form. They are 
colorless, and their motion is less rapid than that of the 
other variety. The total number of both varieties of these 
little bodies in the blood is enormous. It is calculated that 
in a cubic inch of that fluid there are eighty-three mil- 
lions, and at least five hundred times that number in f he 
whole body. 

9. Coagulation. — The blood, in its natural condit. n 
in the body, remains perfectly fluid ; but, within a f e ./ 
minutes after its removal from its proper vessels, whether 
by accident or design, a change takes place. It begins to 
coagulate, or assume a semi-solid consistence. If allowed 
to stand, after several hours it separates into two distinct 
parts, one of them being a dark red jelly, the coagulum, 
or clot, which is heavy and sinks : and the other, a clear, 
straw-colored liquid, called serum, which covers the clot. 
This change is dependent upon the presence in the blood 
of fibrin, which possesses the property of solidifying under 
certain circumstances; one of these circumstances being 
when the blood is separated from living tissues. The color 
of the clot is due to the entanglement of the corpuscles 
with the fibrin. 

10. In this law of the coagulation of the blood is our 
safeguard against death by haemorrhage, or against undue 
loss of blood. If coagulation were impossible, the slight- 

8. White corpuscles ? Total number of corpuscles in the body ? 

9. The blood in its natural condition in the body? Describe the process by 
which the coagulation of blood takes place ? 

1 0. If coagulation were impossible ? How is it in fact ? 



THE CIRCULATION. 105 



est injury in drawing blood would prove fatal. Whereas 
now, in vastly the larger proportion of cases, bleeding 
ceases spontaneously, because the blood, as it coagulates, 
stops the mouths of the injured blood-vessels. In another 
class of cases, where larger vessels are cut or torn, it is 
simply necessary to close them by a temporary pressure ; 
for in a few minutes the clot will form and seal them up. 
In still more serious cases, where the blood-vessel is of 
large size, the surgeon is obliged to tie a " ligature" about 
it, and thus prevent the force of the blood-current from 
washing away the clots, which, forming within and around 
the vessel, would close it effectually. 

11. It is worthy of remark that this peculiarity is early 
implanted in the blood, even before birth, and in advance 
of any existing necessity for it; thus anticipating and 
guarding against danger. But this is not all. Of most 
of the inferior animals, which, as compared with man, are 
quite helpless, the blood coagulates more rapidly, and in 
the case of the birds, almost instantly. The relative 
composition of fluid and coagulated blood may be thus 
represented : 

Fluid Blood. Coagulated Blood. 

Plasma,:;.-^ Serum Serum 

Fibrin--..... 

Corpuscles Corpuscles — l:::::::-Clot. 

12. The Uses of the Blood. — The blood is the great 
provider and purifier of the body. It both carries new 
materials to all the tissues, and removes the worn out par- 
ticles of matter. This is effected by the plasma. It both 
conveys oxygen and removes carbonic acid. This is done 
through the corpuscles. Some singular experiments have 



12. The blood, as a provider and purifier? What uses does the blood sub- 
serve ? Experiments ? Transfusion ? 

5* 



106 THE CIRCULATION. 

been tried to illustrate the life-giving power of the blood. 
An animal that has bled so freely as to be at the point of 
dying, is promptly brought back to life by an operation 
called transfusion, by which fresh blood from a living 
animal is injected into the blood-vessels of his body. 

13. It is related that a dog, deaf and feeble from age, 
had hearing and activity restored to him by the introduc- 
tion into his veins of blood taken from a young dog ; and, 
that a horse, twenty-six years old, having received the blood 
of four lambs acquired new vigor. And further, that a dog, 
just dead from an acute disease, was so far revived by trans- 
fusion, as to be able to stand and make a few movements. 

14. Transfusion has been practised upon man. At one 
time, shortly after Harvey's discovery of the " Circulation 
of the Blood," it became quite a fashionable remedy, it 
being thought possible by it to cure all forms of disease, 
and even to make the old young again. But these claims 
were soon found extravagant, and many unhappy accidents 
occurred in its practice ; so that being forbidden by govern- 
ment and interdicted by the Pope, it rapidly fell into 
disuse. At the present time, however, it is sometimes re- 
sorted to in extreme cases, when there has been a great 
and rapid loss of blood ; and there are upon record several 
instances where, other means having failed, life has been 
restored or prolonged by the operation of transfusion. 

15. This reviving power of the blood seems to reside in 
the corpuscles ; for transfusion, when attempted to be per- 
formed with the serum alone, has, in every case, proved fruit- 
less. Now, though so much depends upon the blood and 
its corpuscles, it is a mistake to suppose that in them alone 
is the seat of life, or that they are, in an exclusive manner, 
alive. All the organs and parts of the body are mutually 
dependent one upon the other ; and the complete usefulness 



1 3 . The case of the deaf and feeble dog ? Horse ? Dead dog ? 

1 4. Transfusion, as a fashionable remedy ? What further of transfusion ? 

1 5 . The seat of the reviving power of the blood ? What further is related ? 



THE CIRCULATION". 107 

of the blood, or of any other part, flows out of the har- 
monious action of all the parts. 

16. Change of Color. — The blood undergoes a variety 
of changes in its journey through the system. As it visits 
the different organs it both gives out and takes up mate- 
rials. In one place it is enriched, in another it is impover- 
ished. By reason of these alterations in its composition, 
the blood also changes its color. In one part of the body 
it is bright red, or arterial ; in another it is dark blue, or 
venous. In the former case it is pure and fit for the sup- 
port of the tissues ; in the latter, it is impure and charged 
with effete materials. (The details of the change from 
dark to bright will be given in the chapter on Respira- 
tion.) 

17. Circulation. — The blood is in constant motion 
during life. From the heart, as a centre, a current is 
always setting toward the different organs; and from these 
organs a current is constantly returning to the heart. In 
this way a ceaseless circular movement is kept up, which is 
called the Circulation of the Blood. This stream of the 
vital fluid is confined to certain fixed channels, the blood- 
vessels. Those branching from the heart are the arteries ; 
those converging to it are the veins. The true course of 
the blood was unknown before the beginning of the seven- 
teenth century. In 1619 it was discovered by the illustri- 
ous William Harvey. Like many other great discoverers, 
he suffered persecution and loss, but unlike some of them, 
he was fortunate enough to conquer and survive opposi- 
tion. He lived long enough to see his discovery universally 
accepted, and himself honored as a benefactor of mankind. 

18. The Heart. — The heart is the central engine of 
the circulation. In this wonderful little organ, hardly 



1 6. Changes in the blood ? What further is stated ? 

17. Motion of the blood? What is meant by the circulation of the blood? 
How confined ? Discovery made by Harvey ? 

18. Office of the heart? Location of the heart ? Its beat? Its shape? Pro- 
tection to the heart ? What else is said in relation to the heart ? 



108 



THE CIRCULATION. 




Fig. 27.— The Organs op Circulation-. " 



THE CIRCULATION. 



100 



larger than a man's fist, resides that sleepless force by 
which, during the whole of life, the current of the blood 
is kept in motion. 
It is placed in the 
middle and front 
part of the chest, 
inclining to the left 
side. The heart- 
beat may be felt and 
heard between the 
fifth and sixth ribs, 
near the breast-bone. 
Its shape is conical, 
with the apex or 
point downward and 
in front (Fig. 28). 
The base, which is 
upward, is attached 
so as to hold it se- 
curely in its place, 
while the apex is 
freely moveable. In 
order that loss of 
power from friction 
may be obviated, the 
heart is enclosed between two layers of serous membrane, 
which forms a kind of sac. This membrane is as smooth 
as satin, and itself secretes a fluid in sufficient quantities 
to keep it at all times well lubricated. The lining mem- 
brane of the heart, likewise, is extremely delicate and 
smooth. 

19. The Cavities of the Heart.— The heart is hol- 
low, and so partitioned as to contain four chambers or 
cavities; two at the base, known as the auricles, from a 




Pig. 28.— The Heart and Large Vessels. 

A, Right Ventricle. D, Left Auricle. 

B, Left " E, Aorta. 

C, Right Auricle. F, Pulmonary Artery. 



19. Formation of the heart ? Right and left heart ? 



110 



THE CIRCULATION. 



fancied resemblance to the ear of a dog, and two at the 
apex or point, called ventricles. An auricle and a ventricle 

on the same side, 
communicate with 
each other, but there 
is no opening from 
side to side. It is 
customary to regard 
the heart as a double 
organ, and to speak 
of its division into 
the right and left 
heart. For while 
both halves act to- 
gether in point of 
time, each half sus- 
tains an entirely dis- 
tinct portion of the 
labor of the circu- 
lation. Thus, the 
right heart always 
carries the dark or 
venous blood, and the left always circulates the bright or 
arterial blood. 

20. If we examine the heart, we at once notice that 
though its various chambers have about the same capacity, 
the walls of the ventricles are thicker and stronger than 
those of the auricles. This is a wise provision, for it is by 
the powerful action of the former that the blood is forced 
to the most remote regions of the body. The auricles, on 
the contrary, need much less power, for they simply dis- 
charge their contents into the cavities of the heart near at 
hand and below them — into the ventricles. 




Fig. 29.— Section op the Heart. 

A, Right Ven tricle. E, F, Inlets to the Ventricles, 

B, Left " G, Pulmonary Artery. 

C, Right Auricle. H, Aorta. 

D, Left Auricle. 



20. Capacity of the chambers of the heart? What wise provision is men- 
tioned ? The auricles f 



THE CIRCULATION. Ill 

21. Action of the Heart. — The substance of the 
heart is of a deep red color, and its fibres resemble those 
of the voluntary muscles by which we move our bodies. 
But the heart's movements are entirely involuntary. The 
advantage of this is evident; for if it depended upon 
us to will each movement, our entire attention would be 
thus engaged, and we would find no time for study, pleas- 
ure, or even sleep. The action of the heart consists in 
alternate contractions and dilatations. During contrac- 
tion the walls come forcibly together, and thus drive out 
the blood. In dilatation, they expand and receive a renewed 
supply. These movements are called systole and diastole. 
The latter may be called the heart's period of repose; and 
although it lasts only during two-fifths of a heart-beat, or 
about a third of a second, yet during the day it amounts 
to more than nine hours of total rest. 

22. A remarkable property of the tissue of the heart is 
its intense vitality. For while it is more constantly active 
than any other organ of the body, it is the last to part 
with its vital energy. This is especially interesting in 
view of the fact that after life is apparently extinguished, 
as from drowning, or poisoning by chloroform, there yet 
lingers a spark of vitality in the heart, which, by contin- 
ued effort, may be fanned into a flame so as to revivify the 
whole body. In cold-blooded animals this irritability of 
the heart is especially remarkable. The heart of a turtle 
will pulsate, and the blood circulate for a week after its 
head has been cut off; and the heart will throb regularly 
many hours after being cut out from the creature's chest. 
The heart of a frog or serpent, separated entirely from the 
body, will contract at the end of ten or twelve hours: that 
of an alligator has been known to beat twenty-eight hours 
after the death of the animal. 

21. Substance of the heart? Its fibres? Its movements? The advantage 
of snch movements ? Action of the heart ? Its period of repose ? 

22. Remarkable property of the tissue of the heart ? How shown ? How in- 
teresting ? In cold-blooded animals ? Heart of a turtle ? Of a frog ? Alligator ? 



112 THE CIRCULATION. 



23. Passage of the Blood through the Heart. — 

Let us now trace the course of the blood through the 
several cavities of the heart. In the first place, the venous 
blood, rendered dark and impure by contact with the 
changing tissues of the body, returns to the right heart 
by the veins. It enters and fills the right auricle during- 
its dilatation : the auricle then contracts and fills the right 
ventricle. Almost instantly, the ventricle contracts forcibly 
and hurries the blood along the great artery of the lungs. 
to be purified in those organs. Secondly, having completed 
the circuit of the lungs, the pure and bright arterial blood 
enters the left auricle. This now contracts and fills the left 
ventricle, which cavity, in its turn, contracts and sends the 
blood forth on its journey again through the system. This 
general direction from right to left is the uniform and un- 
deviating course of heart-currents. 

24. The mechanism which enforces and regulates it, is 
as simple as it is beautiful. Each ventricle has two open- 
ings, an inlet and an outlet, each of which is guarded by 
strong curtains, or valves. These valves open freely to 
admit the blood entering from the right, but close inflex- 
ibly against its return. Thus, when the auricle contracts,, 
the inlet valve opens ; but as soon as the ventricle begins 
to contract, it closes promptly. The contents are then, so 
to speak, cornered, and have but one avenue of escape, 
that through the outlet valve into the arteries beyond. As 
soon as the ventricle begins to dilate again, this valve 
shuts tightly and obstructs the passage. The closing of 
these valves occasions the two heart-sounds, which we hear 
at the front of the chest. 

25. Frequency of the Heart's Action. — The alter- 
nation of contraction and dilation constitutes the heart- 



23. Course of the blood through the heart ? Course of heart-currents ? 

24. Openings of the ventricles ? How guarded ? How do the valves operate ? 
The consequence ? Heart-sounds ? 

25. Heart-beats? The heart as a susceptible organ? Heat, exercise, etc.? 
Posture ? 



THE CIRCULATION. 113 

beats. These follow each other not only with great 
regularity, but with great rapidity. The average number 
in an adult man is about seventy-two in a minute. But 
the heart is a susceptible organ, and many circumstances 
affect its rate of action. Heat, exercise, and food will 
increase its action, as cold, fasting, and sleep will decrease 
it. Posture, too, has a curious influence ; for if while sit- 
ting, the beats of the heart number seventy-one; standing 
erect will increase them to eighty-one, and lying down 
will lower them to sixty-six. 

26. The modifying influence of mental emotions is very 
powerful. Sudden excitement of feeling will cause the 
heart to palpitate, or throb violently. Depressing emotions 
sometimes temporarily interrupt its movements, and the 
person faints in consequence. Excessive joy, grief, or fear, 
has occasionally suspended the heart's action entirely, and 
thus caused death. The rate of the heart-beat may be 
naturally above or below seventy-two. Thus it is stated 
that the pulse of the savage is always slower than that of 
the civilized man. Bonaparte and "Wellington were very 
much alike in their heart's pulsations, which were less than 
fifty in the case of each. 

27. Activity of the Heart. — The average number of 
heart-beats during a lifetime may be considered as at the 
rate of seventy-two per minute, although this estimate is 
probably low ; for during several years of early life the rate 
is above one hundred a minute. In one hour, then, the 
heart pulsates four thousand times ; in a day, one hundred 
thousand times; and in a year, nearly thirty-eight million 
times. If we compute the number during a lifetime, thirty- 
nine years being the present average longevity of civilized 
mankind, we obtain as the vast aggregate, fourteen hun- 
dred millions of pulsations. 



26. Mental emotions ? Sudden excitement ? Excessive joy ? The heart-beat 
rate ? Bonaparte and Wellington ? 

27. Average number of heart-bea^s? In one hour? Year? Lifetime? 



114 THE CIRCULATION. 



28. Again, if we estimate the amount of blood expelled 
by each contraction of the ventricles, at four ounces, then 
the weight of the blood moved during one minute will 
amount to eighteen pounds. In a day it will be about 
twelve tons; in a year, four thousand tons; and in the 
course of a lifetime, over one hundred and fifty thousand 
tons. These large figures indicate, in some measure, the 
immense labor necessary to carry on the interior and vital 
operations of our bodies. In this connection, we call to 
mind the fanciful theories of the ancients in reference to 
the uses of the heart. They regarded it as the abode of 
the soul, and the source of the nobler emotions — bravery, 
generosity, mercy, and love. The words courage and 
cordiality are derived from a Latin word signifying heart. 
Many other words and phrases, as hearty, heart-felt, to learn 
by heart, and large-hearted, show how tenaciously these ex- 
ploded opinions have fastened themselves upon our language. 

29. At the present time the tendency is to ascribe purely 
mechanical functions to the heart. This view, like the 
older one, is inadequate; for it expresses only a small part 
of our knowledge of this organ. The heart is unlike a 
simple machine, because its motive power is not applied 
from without, but resides in its own substance. Moreover, 
it repairs its own waste, it lubricates its own action, and it 
modifies its movements according to the varying needs of 
the system. It is more than a mere force-pump, just as 
the stomach is something more than a crucible, and the 
eye something more than an optical instrument. 

30. The Arteries. — The tube-like canals which carry 
the blood away from the heart are the arteries. Their 
walls are made of tough, fibrous materials, so that they 
sustain the mighty impulse of the heart, and are not rup- 
tured. In common with the heart, the arteries have a del- 



28. Amount of blood expelled? Theories of the ancients? 

29. The tendency at the present time ? Why is this view inadequate ? 

30. What are the arteries ? Their walls ? Their membrane ? 



THE CIRCULATION. 115 

icately smooth lining membrane. They are also elastic, 
and thus re-enforce the action of the heart : they always 
remain open when cut across, and after death are always 
found empty. 

31. The early anatomists observed this phenomenon, 
and supposing that the same condition existed during life, 
came to the conclusion that these tubes were designed to 
act as air-vessels, hence the name artery, from a Greek 
word which signifies containing air. This circumstance 
affords us an illustration of the confused notions of the 
ancients in reference to the internal operations of the 
body. Cicero speaks of the arteries as "conveying the 
breath to all parts of the body," 

32. The arterial system springs from the heart by a 
single trunk, like a minute and hollow tree, with number- 
less branches. As these branches leave the heart they 
divide and subdivide, continually growing smaller and 
smaller, until they can no longer be traced with the 
naked eye. If, then, we continue the examination by the 
aid of a microscope, we see these small branches sending 
off still smaller ones, until all the organs of the body are 
penetrated by arteries. 

33. The Pulse. — With each contraction of the left 
heart, the impulse causes a wave-like motion to traverse 
the entire arterial system. If the arteries were exposed to 
view, we might see successive undulations speeding from 
the heart to the smallest of the branches, in about one- 
sixth part of a second. The general course of the arteries 
is as far as possible from the surface. This arrangement 
is certainly wise, as it renders them less liable to injury, 
the wounding of an artery being especially dangerous. It 
also protects the arteries from external and unequal pres- 
sure, by which the force of the heart Avould be counter- 

31. Early anatomists ? The service of the illustration ? 

32. The arterial system ? The branches and sub-branches of the arteries ? 

33. Successive undulations from the heart ? Course of the arteries? Protec- 
tion of the arteries ? General location of the arteries ? 



116 THE CIRCULATIOX. 

acted and wasted. Accordingly, we generally find these 
vessels hugging close to the bones, or hiding behind the 
muscles and within the cavities of the body. 

34. In a few situations, however, the arteries lie near the 
surface ; and if we apply the finger to any of these parts, 
we will distinctly feel the movement described, taking place 
in harmony with the heart-beat. This is part of the wave- 
motion just mentioned, and is known as the pulse. All 
are more familiar with the pulse at the wrist, in the radial 
artery ; but the pulse is not peculiar to that position, for it 
may be felt in the carotid of the neck, in the temporal at 
the temple, and elsewhere, especially near the joints. 

35. Since the heart-beat makes the pulse, whatever 
affects the former affects the latter also. Accordingly, the 
pulse is a good index of the state of the health, so far as 
the health depends upon the action of the heart. It in- 
forms the physician of the condition of the circulation in 
four particulars: its rate, regularity, force, and fullness; 
and nearly every disease modifies in some respect the con- 
dition of the pulse. A very ingenious instrument, known 
as the sphygmograph, or pulse-writer, has recently been 
invented, by the aid of which the pulse is made to write 
upon paper its own signature, or rather to sketch its own 
profile. This instrument shows with great accuracy the 



Fig. 30.— The Form of the Pulse. 

difference between the pulses of health and those of disease. 
In Fig. 30 is traced the form of the pulse in health, which 
should be read from left to right. That part of the trace 

3 *. Where do the arteries lie ? If we apply the finger ? Pulse ? Where felt ? 
35. The pulse as an index? Of what does it inform the physician ? Instrument 
for recording pulsation ? 



THE CIRCULATION. 



117 



which is nearly perpendicular coincides with the contrac- 
tion of the ventricles ; while the wavy portion marks their 
dilatation. 

36. The Veins. — The vessels which convey the blood 
on its return to the heart are the veins. They begin in 
the several organs of the body, and at first are extremely 
small; but uniting together as they advance, they con- 
stantly increase in size, reminding us of the way in which 
the fine rootlets of the plant join together to form the 
large roots, or of the rills and rivulets that flow together 
to form the large streams and rivers. In structure, the 
veins resemble the arteries, but their walls are compara- 
tively inelastic. They are more numerous, and commu- 
nicate with each other freely in their course, by means of 
interlacing branches. 

37. But the chief point of distinction is in the presence 
of the valves in the veins. These are little folds of mem- 
brane, disposed in such a way, that 
they only open to receive blood . 
flowing toward the heart, and close 
against a current in the opposite 
direction. Their position in the 
veins on the back of the hand may 
be readily observed, if we first ob- p 
struct the return of blood by a cord 
tied around the forearm or wrist. In a few minutes the 
veins will appear swollen, and upon them will be seen 
certain prominences, about an inch apart. These latter 
indicate the location of the valves, or, rather, they show 
that the vessels in front of the valves are distended by the 
blood, which cannot force a passage back through them. 

38. This simple experiment proves that the true direction 
of the venous blood is toward the heart. That the color 




36. What are the veine ? How do they form ? What do they resemble ? 

37. Valves in the veins? What are they? Their position ? Experiment with 
the cord ? 

38. What will be proved by the experiment ¥ What inference is drawn ? 



118 THE CIRCULATION. 



of the blood is dark, will be evident, if we compare the 
hand thus bound by a cord with the hand not so bound. 
It also proves that the veins lie superficially, while the 
arteries are beneath the muscles, well protected from pres- 
sure ; and that free communication exists from one vein to 
another. If now we test the temperature of the constricted 
member by means of a thermometer, we will find that it is 
colder than natural, although the amount of blood is 
larger than usual. From this fact we infer, that whatever 
impedes the venous circulation tends to diminish vitality ; 
and hence, articles of clothing or constrained postures, 
that confine the body or limbs, and hinder the circulation 
of the blood, are to be avoided as injurious to the health. 

39. The Capillaries. — A third set of vessels completes 
the list of the organs of the circulation, namely, the capil- 
lary vessels, so called (from the Latin word capillaris, 
hair-like), because of their extreme fineness. They are, 
however, smaller than any hair, having a diameter of about 
-g-oVo" of an inch, and can only be observed by the use of the 
microscope. These vessels may be regarded as the connect- 
ing link between the last of the arteries and the first of 
the veins. The existence of these vessels was unknown to 
Harvey, and was the one step wanting to complete his 
great work. The capillaries were not discovered until 
1661, a short time after the invention of the microscope. 

40. The circulation of the blood, as seen under the 
microscope, in the transparent web of a frog's foot, is a 
spectacle of rare beauty, possessing more than ordinary 
interest, when we consider that something very similar 
is taking place in our own bodies, on a most magnificent 
scale. It is like opening a secret page in the history of 
our own frames. We there see distinctly the three classes 
of vessels with their moving contents; first, the artery, 



39. Capillaries? How regarded ? Harvey? 

40. The circulation of the blood in the web of a frog's foot? 
How general is the existence of the tissues ? 



THE CIRCULATION". 



119 



with its torrent of blood rushing down from the heart, 
secondly, the vein, with its slow, steady stream flowing in 
the opposite direction ; and between them lies the network 
of capillaries, so fine that the corpuscles can only pass 
through "in single file." The current has here an uncer- 
tain or swaying motion, hurrying first in one direction, then 
hesitating, and then turning back in the opposite direction, 




Fig. 32.— Web op a Frog's Foot, 

slightly magnified. 



Fig. 33.— Margin op Frog's W 
magnified 30 diameters. 



and sometimes the capillaries contract so as to be entirely 
empty. Certain of the tissues are destitute of capillaries ; 
such are cartilage, hair, and a few others on the exterior of 
the body. In all other structures, networks of these vessels 
are spread out in countless numbers : so abundant is the 
supply, that it is almost impossible to puncture any part 
with the point of a needle without lacerating tens, or even . 
hundreds of these vessels. 

41. The capillaries are elastic, and may so expand as to 

produce an effect visible to the naked eye. If a grain of 

sand, or some other foreign particle, lodge in the eye, it will 

become irritated, and in a short time the white of the eye 

'will be "blood-shot." This appearance is due to an in- 

41. Elasticity of the capillaries? Grain of sand in the eye? Blush? Other 



120 THE CIRCULATION". 



crease in the size of these vessels. A blush is another exam- 
ple of this, but the excitement comes through the nervous 
system, and the cause is some transient emotion, either of 
pleasure or pain. Another example is sometimes seen in 
purplish faces of men addicted to drinking brandy; in 
them the condition is a congestion of the capillary circula- 
tion, and is permanent, the vessels having lost their power 
of elastic contraction. 

42. Rapidity of the Circulation. — That the blood 
moves with great rapidity is evident from the almost instant 
Effects of certain poisons, as prussic acid, which act 
through the blood. Experiments upon the horse, dog, 
and other inferior animals, have been made to measure 
its velocity. If a substance, which is capable of a distinct 
chemical reaction (as potassium ferrocyanide, or barium 
nitrate), be introduced into a vein of a horse on one side, 
and blood be taken from a distant vein on the other side, 
its presence may be detected at the end of twenty or thirty- 
two seconds. In man, the blood moves with greater speed, 
and the circuit is completed in twenty-four seconds. 

43. What length of time is required for all the blood of 
the body to make a complete round of the circulation ? 
This question cannot be answered with absolute accuracy, 
since the amount of the blood is subject to continual 
variations. But, if we assume this to be one-eighth of the 
weight of the body, about eighteen pounds, it will be suf- 
ficiently correct for our purpose. Now to complete the 
circuit, this blood must pass once through the left ventricle, 
the capacity of which is two ounces. Accordingly, we find 
that, under ordinary circumstances, all the blood makes one 
complete rotation every two minutes; passing successively 
through the heart, the capillaries of the lungs, the arteries, 
the capillaries of the extremities, and through the veins. 

42. Show what time is required for a given portion of blood to travel once 
around the body. 

43. Time required for all the blood to circulate completely around? 



THE CIRCULATION. 121 



44. Assimilation. — The crowning act of the circula- 
tion, the furnishing of supplies to the different parts of 
the body, is effected by means of the capillaries. The or- 
gans have been wasted by use ; the blood has been enriched 
by the products of digestion. Here, within the meshes of 
the capillary network, the needy tissues and the needed 
nutriment are brought together. By some mysterious 
chemistry, each tissue selects and withdraws from the 
blood the materials it requires, and converts them into a 
substance like itself. This conversion of lifeless food into 
living tissue is called assimilation. The process probably 
takes place at all times, but the period especially favorable 
for it is during sleep. Then the circulation is slower, and 
more regular, and most of the functions are at rest. The 
body is then like some trusty ship, which after a long voy- 
age is " hauled up for repairs." 

45. Injuries to the Blood-vessels. — It is important 
to be able to discriminate between an artery and a vein, in 
the case of a wound, and if we remember the physiology 
of the circulation we may readily do so. For, as we have 
already seen, haemorrhage from an artery is much more 
dangerous than that from a vein. The latter tends to cease 
spontaneously after a short time. The arterial blood flows 
away from the heart with considerable force, in jets; its 
color being bright scarlet. The venous blood flows toward 
the heart from that side of the wound furthest from the 
heart; its stream being continuous and sluggish; its color 
dark. In an injury to an artery, pressure should be made 
between the heart and the wound ; and in the case of a 
vein that persistently bleeds, it should be made upon the 
vessel beyond its point of injury. 

44. What is meant by assimilation ? What can yon say of its use, etc. ? Time I 
45* What if ""•»*-».d of the injuries to the blood-vessels? 



122 REVIEW QUESTIONS. 

QUESTIONS FOR TOPICAL REVIEW. 

PAGB 

1. In what organisms is the so-called circulatory fluid found ? 101 

2. How is it designated in the different organisms ? ' 101 

3. What can you state of the importance of blood to the body ? 101, 105 

4. Of its great abundance, color, and composition ? 101, 102, 107 

5. Describe the corpuscles of the human blood 102, 103, 104 

6. What is said of them in comparison with those of the lower animals ? 103 

7. Of the importance of sometimes detecting human from other blood ? 103 

8. What means have we of detecting blood in spots or stains ? 103, 104 

9. What is meant by coagulation of the blood ? 104 

10. What wisdom is there in the law of the blood's coagulation ? 104, 105 

11. How is this wisdom made manifest ? 105 

12. In what cases is the aid of the surgeon required ? 105 

13. What are the two great uses of the blood ? 105 

14. Through what mediums is the blood provided with new material and re- 

lieved of the old material ? 105 

15. What do you understand by the operation called transfusion ? 106 

16. What cases of transfusion are reported of the lower animals ? 106 

17. What can you state of transfusion as practised upon man ? 106 

18. What further can you say on the subject ? 106, 107 

19. What changes take place in the color of the blood in its journey through 

the system ? 107 

20. State all you can in relation to the circulation of the blood 107 

21. All, in relation to the size, shape, and location of the heart 107, 109 

22. How is the loss of power in the heart movements obviated ? 109 

23. Give a description of the formation of the heart 109, 110, 111 

24. What can you state of the ventricles aud auricles of the heart ? 110 

25. Describe the action of the heart Ill 

26. What special vitality does the tissue of the heart possess ? Ill 

27. State all you can on the subject Ill 

28. Describe the course of the blood through the cavities of the heart 112 

29. Describe the mechanism that regulates the heart-currents 112 

30. How do you account for the two heart-sounds at the front of the chest ? . . . 112 

31. State what you can of the frequency of the heart's action 112, 113 

32. Of the activity of the heart 113, 114 

33. What do you understand by the arteries ? 114, 115 

34. State what you can of the arteries and the arterial system 114, 115 

35. What do you understand by the pulse ? 115, 116 

36. In what part of the body may the pulse be felt ? 116 

37. What further can you state of the pulse ? 1 16, 117 

3S. What are the veins ? 117 

39. Where do they exist, and how are they formed ? 117 

40. Describe the valves of the veins and their uses 117 

41. Now give a full description of the construction of the veins 117 

42. What further can yon s;ate of the veins ? 117, 118 

43. What do you understand by the capillaries ? 118, 119 

44. What service do the capillaries perform V 118, 119, 121 

45. Describe the circulation of the blood in the region of the heart 118, 119 

46. What can you state of the rapidity of the blood's circulation ? 120 

47. Of the process known as assimilation ? 121 

48. Of injuries to the blood-vessels ? 121 



RESPIRATION. 123 



CHAPTER VIII. 

RESPIRATION. 

The Objects of Respiration — The Lungs — The Air-Passages — The Move- 
ments of Respiration — Expiration and Inspiration — The Frequency 
of Respiration — Capacity of the Lungs — The Air we breathe — 
Changes in the Air from Respiration — Changes in the Blood — In- 
terchange of Gases in the Lungs — Comparison between Arterial and 
Venous Blood — Respiratory Labor — Impurities of the Air — Bust — 
Carbonic Acid — Effects of Impure Air — Nature's Provision for 
Purifying tlie Air — Ventilation — Animal Heat — Spontaneous Com- 



1. The Object of Respiration. — In one set of capil- 
laries, or hair-like vessels, the blood is impoverished for the 
support of the different members and organs of the body. 
In another capillary system the blood is refreshed and again 
made fit to sustain life. The former belongs to the greater 
or systemic circulation ; the latter to the lesser or pulmo- 
nary, so called from pulmo, the lungs, in which organs it 
is situated. The blood, as sent from the right side of the 
heart to the lungs, is venous, dark, impure, and of a nature 
unfit to circulate again through the tissues. But, when 
the blood returns from the lungs to the left side of the 
heart, it has become arterial, bright, pure, and no longer 
hurtful to the tissues. This marvellous purifying change 
is effected by means of the very familiar act of respiration, 
or breathing. 

2. The Lungs. — The lungs are the special organs of 
respiration. There are two of them, one on each side of 
the chest, which cavity they, with the heart, almost wholly 
occupy. The lung-substance is soft, elastic, and sponge- 
like. Under pressure of the finger, it crepitates, or crackles, 
and floats when thrown into water ; these properties being 

1 . Difference between the two sets of capillaries ? Change effected by respira- 
tion or breathing ? 

2. What are the lunge? How many lungs are there? Lung-substance? Its 
properties ? The pleura ? 



324 



RESPIRATION. 



due to the presence of air in the minute air-cells of the 
lungs. To facilitate the movements necessary to these 
organs, each of them is provided with a double covering of 
an exceedingly smooth and delicate membrane, called the 




Fig. 34. — Organs of the Chest. 

A, Lunge. D, Pulmonary Artery. 

B, Heart. E, Trachea. 

pleura. One layer of the pleura is attached to the walls 
of the chest, and the other to the lungs ; and they glide, 
one upon the other, with utmost freedom. Like the mem- 
brane which envelops the heart, the pleura secretes its own 
lubricating fluid, in quantities sufficient to keep it alwaye 
moist. 

3. The Air-Passages. — The lungs communicate with 
the external air by means of certain air-tubes, the longest of 



3. Communication of the lungs with the external air? Bronchial tubes ? 



RESPIRATION. 



125 



which, the trachea, or windpipe, runs along the front of the 
neck (Fig. 34, E, and 35) .With- 
in the chest this tube divides 
into two branches, one entering 
each lung; these in turn give 
rise to numerous branches, or 
bronchial tubes, as they are 
called, which gradually dimin- 
ish in size until they are about 
one-twenty-fifth of an inch in 
diameter. Each of these ter- 
minates in a cluster of little 
pouches, or "air-cells," having 
very thin walls, and covered 
with a capillary network, the 
most intricate in the body 
(Fig. 36). 




4. These tubes are some- 
what flexible, sufficiently so to 
bend when the parts move in 
which they are situated; but 
they are greatly strengthened 
by bands or rings of cartilage 
which keep the passages always 
open; otherwise there would 
be a constantly-recurring ten- 
dency to collapse after every 
breath. The lung-substance 
essentially consists of these 
bronchial tubes and terminal 
air-cells, with the blood-ves- 
sels ramifying about them 
(Fig. 37). At the top of the 
trachea is the larynx, a sort of 



>.— Larynx, Trachea, and 
Bronchial Tubes. 




4. Office of the bronchial tubes ? What further can you state of them ? 



126 



RESPIRATION. 



box of cartilage, across which are stretched the vocal cords. 
Here the voice is produced chiefly by the passage of the 
jespired air over these cords, causing them to vibrate. 




Fig. 37.— Section op the Lungs. 

5. Over the opening of the larynx is found the epiglottis, 
which fits like the lid of a box at the entrance to the 
Inngs, and closes during the act of swallowing, so that 
food and drink shall pass backward to the oesophagus, or 
gullet (Fig. 38). Occasionally it does not close in time, 
and some substance intrudes within the larynx, when we at 
once discover, by a choking sensation, that ''something has 
gone the wrong way," and, by coughing, we attempt to ex- 
pel the unwelcome intruder. The epiglottis is one of the 
many safeguards furnished by nature for our security and 



5, The epiglottis ? When it does not close in time, what is the consequence? 



RESPIRATION. 



127 



comfort, and is planned and put in place long before these 
organs are brought into actual use in breathing and in 
taking food. 



6-~f 




Fig. 38.— Section of Mouth and Throat. 

A, The Tongue. C, Vocal Cord. N, Trachea. 

B, The Uvula. E, Epiglottis. O, (Esophagus. 

L, Larynx. 



6. The air -passages are lined tnrough nearly their 
whole extent with mucous membrane, which maintains 
these parts in a constantly moist condition. This mem- 
brane has a peculiar kind of cells upon its outer sur- 



6. Lining of the air-passages? Ciliated cells? Their uses? The three dis- 
eases of the lungs ? 



128 



RESPIRATION. 




-Ciliated Cells. 



face. If examined under a powerful microscope, we may 
see, even for a considerable time after their removal from 
the body, that these cells have minute hair-like processes 
in motion, which wave like a field of grain under the 
influence of a breeze (Fig. 39). This is a truly beauti- 
ful sight; and since it is found that these little cilia, as 
they are called, always produce currents in one direction, 
from within Outward, it is probable that they serve a 
useful purpose in catching and 
carrying away from the lungs 
dust and other small particles 
drawn in with the breath (Fig. 
39). The three diseases which 
more commonly affect the lungs, 
as the result of exposure, are 
• pneumonia, or inflammation of 
the lungs, implicating principally 
the air-cells; bronchitis, an inflammation of the large bron- 
chial tubes ; and pleurisy, an inflammation of the investing 
membrane of the lungs, or pleura. Among the young, an 
affection of the trachea takes place, known as croup. 

7. The Movements of Respiration. — The act of 
breathing has two parts — (1), inspiration, or drawing 
air into the lungs, and (2), expiration, or expelling it 
from the lungs again. In inspiration, the chest extends 
in its length, breadth, and height, or width. We can 
prove that this is the case as regards the two latter, by 
observing the effect of a deep breath. The ribs are ele- 
vated by means of numerous muscles, some of which oc- 
cupy the entire spaces between those bones. But the 
increase in length, or vertically, is not so apparent, as it is 
caused by a muscle within the body called the diaphragm, 
it being the thin partition which separates the chest from 
the abdomen, rising like a dome within the chest. (Fig. 16). 



7. The act of breathing ? Extension of the chest by breathing ? 



RESPIRATION. 129 



8. With every inspiration, the diaphragm contracts, and 
in so doing, approaches more nearly a plane, or horizontal, 
surface, and thus enlarges the capacity of the ckest. 
Laughing, sobbing, hiccoughing, and sneezing are caused 
by the spasmodic or sudden contraction of the diaphragm. 
The special power of this muscle is important in securing 
endurance, or "long wind," as it is commonly expressed; 
which may be obtained mainly by practice. It is possessed 
in a marked degree by the mountaineer, the oarsman, and 
the trained singer. As the walls of the chest extend, the 
lungs expand, and the air rushes in to fill them. This 
constitutes an inspiration. The habit of taking frequent 
and deep inspirations, in the erect position, with the 
shoulders thrown back, tends greatly to increase the ca- 
pacity and power of the organs of respiration. 

9. Expiration is a less powerful act than inspiration. 
The diaphragm relaxes its contraction, and ascends in the 
form of a dome; the ribs descend and, con tract the chest; 
while the lungs themselves, being elastic, assist to drive 
out the air. The latter passes out through the same chan- 
nels by which it entered. At the end of each expiration 
there is a pause, or period of repose, lasting about as long 
as the period of action. 

10. Frequency of Respiration. — It is usually esti- 
mated that we breathe once during every four beats of the 
heart, or about eighteen times in a minute. There is, of 
course, a close relation between the heart and lungs, and 
whatever modifies the pulse, in like manner affects the 
breathing. When the action of the heart is hurried, a 
larger amount of blood is sent to the lungs, and, as the 
consequence, they must act more rapidly. Occasionally, 
the heart beats so very forcibly that the lungs cannot keep 
pace with it, and then we experience a peculiar sense of 

8. Contraction of the diaphragm ? Power of the diaphragm? Effects of ex- 
tending the wails of the chest ? The habit of taking frequent and deep inspirations ? 

9. Expiration ? The mechanism of expiration ? 

10. Frequency of respiration ? Effect of hurried action of the heart? 



130 RESPIRATION. 

distress from the want of air. This takes place when we 
run until we are "out of breath." At the end of every 
fifth or sixth breath, the inspiration is generally longer 
than usual, the effect being to change more completely the 
air of the lungs. 

11. Although, as a general rule, the work of respiration 
goes on unconsciously and without exertion on our part, 
it is nevertheless under the control of the will. We can 
increase or diminish the frequency of its acts at pleasure, 
and we can "hold the breath," or arrest it altogether 
for a short time. From twenty to thirty seconds is 
ordinarily the longest period in which the breath can be 
held; but if we first expel all the impure air from the 
lungs, by taking several very deep inspirations, the time 
may be extended to one and a half or even two minutes. 
This should be remembered, and acted upon, before pass- 
ing through a burning building, or any place where the 
air is very foul. The arrest of the respiration may be still 
further prolonged by training and habit ; thus it is said, 
the pearl-fishers of India can remain three or four minutes 
under water without being compelled to breathe. 

12. Capacity of the Lungs. — The lungs are not 
filled and emptied by each respiration. For while their 
full capacity, in the adult, is three hundred and twenty 
cubic inches, or more than a gallon, the ordinary breath- 
ing air is only one-sixteenth part of that volume, or twenty 
cubic inches, being two-thirds of a pint. Accordingly, a 
complete renovation, or rotation, of the air of the lungs 
does not take place more frequently than about once in a 
minute ; and by the gradual introduction of the external 
air, its temperature is considerably elevated before it 
reaches the delicate pulmonary capillaries. In tranquil 
respiration, less than two-thirds of the breathing power is 



1 1 . Respiration controlled by the will ? Advantage of the knowledge to us ? 

12. Capacity of the lungs? Time required to renovate the air in the lunge? 
In tranquil respiration ? Importance of the provision ? 



RESPIRATION". ' 131 



called into exercise, leaving a reserve capacity of about one 
hundred and twenty cubic inches, equivalent to three and 
one half pints. This provision is indispensable to the con- 
tinuation of life ; otherwise, a slight embarrassment of res- 
piration, by an ordinary cold, for instance, would suffice 
to cut off the necessary air, and the spark of life would 
be speedily extinguished. 

13. The Air we breathe. — The earth is enveloped 
on all sides by an invisible fluid, called the atmosphere. 
It forms a vast and shoreless ocean of air, forty-five miles 
deep, encircling and pervading all objects on the earth's 
surface, which is absolutely essential for the preservation of 
all vegetable and animal life, — in the sea, as well as on the 
land and in the air. At the bottom, or in the lower strata 
of this aerial ocean, we move and have our being. Per- 
fectly pure water will not support marine life, for a fish 
may be drowned in water from which the air has been ex- 
hausted, just as certainly as a mouse, or any other land 
animal, will perish if put deeply into the water for a length 
of time. The cause is the same in both cases : the animal 
is deprived of the requisite amount of air. It is also stated, 
that if the water-supply of the plant be deprived of air, its 
vital processes are at once checked. 

14. The air is not a simple element, as the ancients sup- 
posed, but is formed by the mingling of two gases, known 
to the chemist as oxygen and nitrogen, in the proportion 
of one part of the former to four parts of the latter. These 
gases are very unlike, being almost opposite in their prop- 
erties : nitrogen is weak, inert, and cannot support life ; 
while oxygen is powerful, and incessantly active ; and is the 
essential element which gives to the atmosphere its power 
to support life and combustion. The discovery of this fact 
was made by the French chemist, Lavoisier, in 1778. 



13. The atmosphere ? How high or deep ? How essential to life ? Marine life 
in perfectly pure water and air ? 

14. Composition of the air ? Properties of the two gases ? 



132 RESPIRATION. 



15. Changes in the Air from Respiration. — Air 

that has been once breathed is no longer fit for respiration. 
An animal confined within it will sooner or later die; so 
too, a lighted candle placed in it will be at once extin- 
guished. If we collect a quantity of expired air and ana- 
lyze it, we shall find that its composition is not the same 
as that of the inspired air. When the air entered the 
lungs it was rich in oxygen ; now it contains twenty-five 
per cent, less of that gas. Its volume, however, remains 
nearly the same ; its loss being replaced by another and 
very different gas, which the lungs exhaled, called carbonic 
acid, or, as the chemist terms it, carbon dioxide. 

16. The expired air has also gained moisture. This is 
noticed when we breathe upon a mirror, or the window- 
pane, the surface being tarnished by the condensation of 
the watery vapor exhaled by the lungs. In cold weather, 
this causes the fine cloud which is seen issuing from the 
nostrils or mouth with each expiration, and contributes in 
forming the feathery crystals of ice which decorate our 
window-panes on a winter's morning. 

17. This watery vapor contains a variable quantity of 
animal matter, the exact nature of which is unknown; but 
when collected it speedily putrefies and becomes highly 
offensive. From the effects, upon small animals, of con- 
finement in their own exhalations, having at the same 
time an abundant supply of fresh air, it is believed that 
the organic matters thrown off by the lungs and skin 
are direct and active poisons; and that to such emana- 
tions from the body, more than to any other cause, are 
due the depressing and even fatal results which follow the 
crowding of large numbers of persons into places of lim- 
ited capacity. 

1 5 . Air once breathed ? An animal in it ? A candle ? Analysis of expired air f 
Change in volume ? 

1 6. What else has the expired air gained ? When and where noticed ? 

1 7. Nature of the watery vapor ? Its effects upon animals ? 



KESPIKATIOif. 133 

18. History furnishes many painful instances of the ill 
effects of overcrowding. In 1756, of one hundred and 
forty-six Englishmen imprisoned in the Black Hole of 
Calcutta, only twenty-three, at the end of eight hours, 
survived. After the battle of Austerlitz, three hundred 
prisoners were crowded into a cavern, where, in a few 
hours, two-thirds of their number died. On board a 
steam-ship, during a stormy night, one hundred and 
fifty passengers were confined in a small cabin, but 
when morning came, only eighty remained alive. 

19. Changes in the Blood from Respiration. — 
The most striking change which the blood undergoes by 
its passage through the lungs, is the change of color from 
a dark blue to bright red. That this change is dependent 
upon respiration has been fully proved by experiment. 
If the trachea, or windpipe, of a living animal be so com- 
pressed as to exclude the air from the lungs, the blood in 
the arteries will gradually grow darker, until its color is 
the same as that of the venous blood. When the pressure 
is removed the blood speedily resumes its bright Hue. 
Again, if the animal be made to breathe an atmosphere 
containing more oxygen than atmospheric air, the color 
changes from scarlet to vermilion, and becomes even 
brighter than arterial blood. This change of color is not 
of itself a very important matter, but it indicates a most 
important change of composition. 

20. The air, as we have seen, by respiration loses oxy- 
gen and gains carbonic acid : the blood, on the contrary, 
gains oxygen and loses carbonic acid. The oxygen is the 
food of the blood corpuscles; while the articles we eat and 
drink belong more particularly to the plasma of the blood. 
The air, then, it is plain, is a sort of food, and we should 



18. Give some of the instances furnished by history. 

19. Change in the blood from blue to red. Upon what does the change depend ? 
How shown ? 

20. What does the air lose and gain by respiration ? What, the blood ? Air aa 
food? 



134 RESPIRATION. 

undoubtedly so regard it, if it were not for the fact that 
we require it constantly, instead of taking it at stated in- 
tervals, as is the case with our articles of diet. Again, as 
the demand of the system for food is expressed by the sen- 
sation of hunger, so the demand for air is marked by a 
painful sensation called suffocation. 

21. Interchange of Gases in the Lungs. — As the 
air and the blood are not in contact, they being separated 
from each other by the walls of the air-cells and of the 
blood-vessels, how can the two gases, oxygen and carbonic 
acid, exchange places ? Moist animal membranes have a 
property which enables them to transmit gases through 
their substance, although they are impervious to liquids. 
This may be beautifully shown by suspending a bladder 
containing dark blood in a jar of oxygen. At the end of 
a few hours the oxygen will have disappeared, the blood 
will be brighter in color, and carbonic acid will be found 
in the jar. 

22. If this interchange takes place outside of the body, 
how much more perfectly must it take place within, where 
it is favored by many additional circumstances! The 
walls of the vessels and the air-cells offer no obstacle to 
this process, which is known as gaseous diffusion. Both 
parts of the process are alike of vital importance. If oxy- 
gen be not received, the organs cease to act ; and if car- 
bonic acid be retained in the blood, its action is that of a 
poison ; unconsciousness, convulsions, and death follow- 
ing. 

23. Difference between Arterial and Venous 
Blood. — The following table presents the essential points 
of difference in the appearance and composition of the 
blood, before and after its passage through the lungs : — 



21 . Moist animal membranes ? How shown with the bladder ? 

22. Gaseous diffusion? If oxygen be not received? If carbonic acid be re- 
tained? 

23. Difference in the appearance and composition of the blood? Temperature 
of the blood ? The blood while passing through the lungs ? The consequence ? 



RESPIRATION. 135 

Venous Blood. Arterial Blood. 

Color, Dark blue, Scarlet. 

Oxygen, 8 per cent., 18 per cent. 

Carbonic Acid, 15 to 20 per cent., 6 per cent, or less. 

Water, More, Less. 

The temperature of the blood varies considerably; but 
the arterial stream is generally warmer than the venous. 
The blood imparts heat to the air while passing through 
the lungs, and consequently the contents of the right side 
of the heart has a higher temperature than the contents 
on the left side. 

24. By means of the spectroscope, we learn that the 
change of color in the blood has its seat in the corpuscles ; 
and that, according as they retain oxygen, or release it, they 
present the spectrum of arterial or venous blood. There 
evidently exists, on the part of these little bodies, an affin- 
ity for this gas, and hence they have been called " carriers 
of oxygen." It was long ago thought that blue blood was 
a trait peculiar to persons of princely and royal descent, 
and boastful allusions to the " sang azure" of kings and 
nobles are quite often met with. Physiology, however, in- 
forms us that blue blood flows in the veins of the low as 
well as the high, and that so far from its presence indicat- 
ing a mark of purity, it, in reality, represents the waste and 
decay of the system. 

25. Amount of Respiratory Labor. — During or- 
dinary calm respiration, we breathe eighteen times in a 
minute ; and twenty cubic inches of air pass in and out of 
the lungs with every breath. This is equivalent to the use 
of three hundred and sixty cubic inches, or more than ten 
pints of air each minute. From this Ave calculate that the 
quantity of air which hourly traverses the lungs is about 
thirteen cubic feet, or seventy-eight gallons ; and daily, not 



24. What do we learn by means of the spectroscope ? " Carriers of oxygen ? 
Blue blood in the system ? 

25. The amount of air that passes in and out of the lungs ? 



136 RESPIRATION. 

less than three hundred cubic feet, an amount nearly equal 
to the contents of sixty barrels. 

26. Of this large volume of air five per cent, is absorbed 
in its transit through the lungs. The loss thus sustained is 
almost wholly of oxygen, and amounts to fifteen cubic feet 
daily. The quantity of carbonic acid exhaled by the lungs 
during the day is somewhat less, being twelve cubic feet. 
Under the influence of excitement or exertion, the breath- 
ing becomes more frequent and more profound ; and then 
the internal respiratory work increases proportionately, 
and may even be double that of the above estimate. It 
has been estimated that in drawing a full breath, a man 
exerts a muscular force equal to raising two hundred 
pounds placed upon the chest. 

27. Impurities of the Air. — The oxygen in the at- 
mosphere is of such prime importance, and its proportion 
is so nicely adjusted to the wants of man, that any gas or 
volatile substance which supplants it must be regarded as 
a hurtful impurity. All gases, however, are not alike in- 
jurious. Some, if inhaled, are necessarily fatal; arsen- 
uretted hydrogen being one of these, a single bubble of 
which destroyed the life of its discoverer, Gehlen. Others 
are not directly dangerous, but by taking the place of 
oxygen, and excluding it from the lungs, they become so. 
Into this latter class we place carbonic acid. 

28. Most of the actively poisonous gases have a pungent 
or offensive odor; and, as may be inferred, most repugnant 
odors indicate the presence of substances unfit for respira- 
tion. Accordingly, as we cannot see or taste these impu- 
rities, the sense of smell is our principal safeguard against 
them ; and we recognize the design which has planted this 
sense, like a sentinel at the proper entrance of the air- 



26. Air absorbed in its transit through the lungs? The loss ? Carbonic acid 
exhaled ? Effect of excitement or exertion ? What estimate ? 

27. Importance of the oxygen in the atmosphere? Injurious character of 
gases ? 

28. Pungency of gases ? The inference ? Our safeguard? 



RESPIRATION. 137 



passages, the nostrils, to give us warning of approaching 
harm. Take, as an example, the ordinary illuminating 
gas of cities, from which so many accidents happen. How 
many more deaths would it cause if, when a leak occurs, 
we were not able to discover the escape of the gas by means 
of its disagreeable odor. 

29. Organic matters exist in increased measure in the 
expired breath of sick persons, and impart to it, at times, a 
putrid odor. This is especially true in diseases which, 
like typhus and scarlet fever, are referable to a blood 
poison. In such cases the breath is one of the means by 
which nature seeks to expel the offending material from 
the system. Hence, those who visit or administer to fever- 
sick persons should obey the oft-repeated direction, " not 
to take the breath of the sick." At such times, if ever, 
fresh air is demanded, not alone for the sick, but as well 
for those who are in attendance. 

30. Dust in the Air. — Attention has lately been di- 
rected to the dust, or haze, that marks the ray of sunshine 
across a shaded room. Just as, many years ago, it was dis- 
covered that myriads of animalcule infested much of the 
water we drank, so now the microscope reveals "the gay 
motes that dance along a sunbeam" to be, in part, com- 
posed of multitudes of animal and vegetable forms of a 
very low grade, the germs of fermentation and putrefac- 
tion, and the probable sources of disease. 

31. It is found that the best filter by which to separate 
this floating dust from the air is cotton wool, although a 
handkerchief will imperfectly answer the same purpose. 
In a lecture on this subject by Prof. Tyndall, he remarks 
that, " by breathing through a cotton wool respirator, the 
noxious air of the sick room is restored to practical purity. 
Thus filtered, attendants may breathe the air unharmed. 



29. The air of rooms in which fever-sick persons are confined ? 

30. Animalcula in the water '( Dust in the air? 

3 1 . The best air filter ? The remarks of Prof. Tyndall ? 



138 RESPIRATION. 



In all probability, the protection of the lungs will be the 
protection of the whole system. For it is exceedingly 
probable that the germs which lodge in the air-passages 
are those which sow epidemic disease in the body. If this 
be so, then disease can certainly be warded off by filters of 
cotton wool. By this means, so far as the germs are con- 
cerned, the air of the highest Alps may be brought into 
the chamber of the invalid." 

32. Carbonic Acid in the Air. — We have already 
spoken of this gas as an exhalation from the lungs, and a 
source of impurity ; but it exists naturally in the atmos- 
phere in the proportion of one half part per thousand. In 
volcanic regions it is poured forth in enormous quantities 
from fissures in the earth's surface. Being heavier than 
air, it sometimes settles into caves and depressions in the 
surface. It is stated that in the island of Java, there is a 
place called the " Valley of Poison," where the ground is 
covered with the bones of birds, tigers, and other wild ani- 
mals, which were suffocated by carbonic acid while passing. 
The Lake Avernus, the fabled entrance to the infernal re- 
gions, was, as its name implies, bird-less, because the birds, 
while flying over it, were poisoned by the gas and fell dead 
into its waters. In mines, carbonic acid forms the dreaded 
choke-damp, while carburetted hydrogen is the fire-damp. 

33. In the open air, men seldom suffer from carbonic 
acid, for, as we shall see presently, nature provides for its 
rapid distribution, and even turns it to profitable use. 
But its ill effects are painfully evident in the abodes of 
men, in which it is liable to collect as the waste product of 
respiration and of that combustion which is necessary for 
lighting and warming our homes. A man exhales, during 
repose, not less than one-half cubic foot of carbonic acid 
per hour. One gas-burner liberates five cubic feet in the 



32. Carbonic acid in volcanic regions ? In Java? At Lake Avernns ? In mines f 

33. In the open air? Amount of carbonic acid exhaled by a man? A gas- 
burner ? A room fire ? From furnaces ? 



RESPIKATIOK. 139 

same time, and spoils about as much air as ten men. A 
fire burning in a grate or stove emits some gaseous impur- 
ity, and at the same time abstracts from the air as much 
oxygen as twelve men would consume in the same period, 
thus increasing the relative amount of carbonic acid in 
the air. From furnaces, as ordinarily constructed, this gas, 
with other products of combustion, is constantly leaking 
and vitiating the air of tightly-closed apartments. 

34. Effects of Impure Air. — Carbonic acid, in its 
pure form, is irrespirable, causing rapid death by suffoca- 
tion. Air containing forty parts per thousand of this gas 
(the composition of the expired breath) extinguishes a 
lighted candle, and is fatal to birds ; when containing one 
hundred parts, it no longer yields oxygen to man and 
other warm-blooded animals; and is of course at once 
fatal to them. In smaller quantities, this gas causes head- 
ache, labored respiration, palpitation, unconsciousness, and 
convulsions. 

35. In crowded and badly ventilated apartments, where 
the atmosphere relatively contains from six to ten times 
the natural amount of carbonic acid, the contaminated air 
causes dulness, drowsiness, and faintness; the dark, im- 
pure blood circulating through the brain, oppressing that 
organ and causing it to act like a blunted tool. This is a 
condition not uncommon in our schools, churches, court- 
rooms, and the like, the places of all others where it is 
desirable that the mind should be alert and free to act; 
but, unhappily, an unseen physiological cause is at work, 
dispensing weariness and stupor over juries, audience, and 
pupils. 

36. Another unmistakable result of living in and breath- 
ing foul air is found in certain diseases of the lungs, 
especially consumption. For many years the barracks of 



34, Effects of inhaling carbonic acid alone ? In small quantities? 

35, Effects of the air in crowded and badly ventilated rooms? 

36, A cause of consumption ? How was the fact illustrated ? 



140 RESPIKATIOK. 

the British army were constructed without any regard to 
ventilation; and during those years the statistics showed 
that consumption was the cause of a very large proportion 
of deaths. At last the government began to improve the 
condition of the buildings, giving larger space and air- 
supply; and as a consequence, the mortality from con- 
sumption has diminished more than one-third. 

37. The lower animals confined in the impure atmos- 
phere of menageries, contract the same diseases as man. 
Those brought from a tropical climate, and requiring arti- 
ficial warmth, generally die of consumption. In the Zoo- 
logical gardens of Paris, this disease affected nearly all 
monkeys, until care was taken to introduce fresh air by 
ventilation; and then it almost wholly disappeared. The 
tendency of certain occupations to shorten life is well 
known; disease being occasioned by the fumes and dust 
which arise from the material employed, in addition to the 
unhealthful condition of the workshop or factory where 
many hours are passed daily. 

38. The following table shows the comparative amount 
of carbonic acid in the air under different conditions and 
the effects sometimes produced: — 

Proportion of Carbonic Acid. in iooo parts of Air. 

Air of country 4 

" "city 5 

In hospital, well ventilated 6 

In school, church, etc., fairly ventilated 1.2 to 2.5 

In court-house, factory, etc., without ventilation 4. to 40. 

In bedroom, before being aired 4.5 

In bedroom, after being aired 1.5 

Constantly breathed, causing ill health 2. 

Occasionally breathed, causing discomfort 3. 

Occasionally breathed, causing distress 10. 

Expired air 40. 

Air no longer yielding oxygen 100. 

37, How, in the case of the lower animals ? Tendency of certain occupations ? 

38, Give the fact as set forth in the table. 



RESPIKATIOK. 141 



39. Nature's Provision for Purifying the Air. — 

We have seen that carbonic acid is heavier than air, and 
is poisonous. Why, then, does it not sink upon and over- 
whelm mankind with a silent, invisible wave of death ? 
Among the gases there is a more potent force than gravity, 
which forever precludes such a tragedy. It is known as 
the diffusive power of gases. It acts according to a defi- 
nite law, and with a resistless energy compelling these 
gases, when in contact, to mingle until they are thor- 
oughly diffused. The added influence of the winds is 
useful, by insuring more rapid changes in the air; air in 
motion being perfectly wholesome. The rains also wash 
the air. 

40. We have seen that the whole animal creation is con- 
stantly abstracting oxygen from the atmosphere, and as 
constantly adding to it vast volumes of a gas injurious alike 
to all, even in small quantities. How, then, does the air re- 
tain, unchanged, its life-giving properties? The constant 
purity of the air is secured by means of the vegetable cre- 
ation. Carbonic acid is the food of the plants, and oxygen 
is its waste product. The leaves are its lungs, and under 
the stimulus of sunlight a vegetable respiration is set in 
motion, the effects of which are just the reverse of the 
function we have been considering. Thus nature purifies 
the air, and at the same time builds up beautiful and use- 
ful forms of life from elements of decay. 

41. In the sea, as in the air, the same circle of changes 
is observed. Marine animals consume oxygen and give off 
carbonic acid; while marine plants consume carbonic acid 
and liberate oxygen. Taking advantage of this fact, we 
may so arrange aquaria with fishes and sea-plants, in their 
proper combinations, so that each supplies the needs of the 
other, and the water requires seldom to be renewed. This 

39, What can you state of the diffusive power of gases ? The added influence 
of the winds ? 

40, How is the constant purity of the air secured ? Explain the process ? 

41, What process occurs in the sea ? How is the fact illustrated ? 



142 RESPIRATION. 



affords us, on a small scale, an illustration of the mutual 
dependence of the two great kingdoms of nature; as well 
as of those compensating changes which are taking place 
on such a grand scale in the world about us. 

42. Ventilation. — Since the external atmosphere, as 
provided by nature, is always pure, and since the air in our 
dwellings and other buildings is almost always impure, it 
becomes imperative that there should be a free communica- 
tion from the one to the other. This we aim to accomplish 
by ventilation. As our houses are ordinarily constructed, 
the theory of ventilation, "to make the internal as pure as 
the external air," is seldom carried out. Doors, windows, 
and flues, the natural means of replenishing the air, are 
too often closed, almost hermetically, against the precious 
element. Special means, or special attention, must there- 
fore be used to secure even a fair supply of fresh air. This 
is still more true of those places of public resort, where 
many persons are crowded together. 

43. If there are two openings in a room, one as a vent 
for foul air, and the other an inlet for atmospheric air, 
and if the openings be large, in proportion to the number 
of air consumers, the principal object will be attained. 
Thus, a door and window, each opening into the outer air, 
will ordinarily ventilate a small apartment; or a window 
alone will answer, if it be open both above and below, and 
the open space at each end be not less than one inch for 
each occupant of the room, when the window is about a 
yard wide. The direction of the current is generally from 
below upward, since the foul, heated air tends to rise; 
but this is not essential. Its rate need not be rapid ; a 
"draught," or perceptible current, is never necessary to 
good ventilation. The temperature of the air admitted 
may be warm or cold. It is thought by many that if the 

42. Character of the external air ? Of the air in our dwellings ? What hecomes 
imperative ? Imperfect ventilation of our dwellings? 

43. What hints are given for the ventilation of our dwellings ? 



RESPIRATION/. 143 

air is cold, it is pure ; but this is an error, since cold air 
will receive and retain the same impurities as warm air. 

44. Shall we open our bedrooms to the night air ? Flor- 
ence Nightingale says, in effect, that night air is the only 
air that we can then breathe. " The choice is between pure 
air without and impure air within. Most people prefer the 
latter, — an unaccountable choice. An open window, most 
nights in the year, can hurt no one. In great cities, night 
air is the best and purest to be had in twenty-four hours. 
I could better understand, in towns, shutting the windows 
during the day than during the night." 

45. Animal Heat. — Intimately connected with respi- 
ration is the production of animal heat, or the power of 
maintaining the temperature of the body above that of the 
medium in which the creature moves; thus, the bird is 
warmer than the air, and the fish than the water. This 
elevation of temperature is a result of the various chemi- 
cal changes which are constantly taking place in the system. 
Although common to all animals, in a greater or less 
degree, heat is not peculiar to them ; since plants also gen- 
erate it, especially at the time of sprouting and flowering. 
If a thermometer be placed in a cluster of geranium flow- 
ers, it will indicate a temperature several degrees above 
that of the surrounding air. 

46. Among animals great differences are noticed in this 
respect, but the degree of heat produced is always propor- 
tional to the activity of respiration and the amount of 
oxygen consumed. Accordingly, the birds, whose habits 
are extremely active, and whose breathing capacity is the 
greatest, have uniformly the highest temperature. Slug- 
gish animals, on the contrary, as frogs, lizards, and snakes, 
have little need for oxygen, and have incompletely de- 



44. State what Florence Nightingale says ahout inhaling night air? 

45. Warmth of the bird as compared with that of the air? Of the fish and 
the water ? Heat in animals and plants ? How illustrated with the thermometer ? 

46. Amount of heat in animals, how apportioned ? As regards the birds ? 
Frogs, and other sluggish animals ? Arrangement made by zooligsts ? 



144 RESPIRATION. 

veloped lungs ; these animals are cold to the touch, that is, 
they have relatively a lower temperature than man, and 
their positive temperature is but little above that of the 
external air. Accordingly, zoologists have so arranged the 
•animal kingdom that warm-blooded animals, including 
man, the birds, and the quadrupeds, are classified together ; 
while the cold-blooded animals, such as the fish, tortoise, 
frog, and all that have no vertebral column, are classed 
by themselves. 

47. The temperature of the human body is about 100° 
Fahrenheit, and remains about the same through winter 
and summer, in the tropics as well as in the frozen regions 
of the north. It may change temporarily within the range 
of about twelve degrees; but any considerable, or long-con- 
tinued elevation or diminution of the bodily heat is certain 
to result disastrously. 

48. Man is able to adapt himself to all extremes of 
climate; and, in fact, by means of clothing, shelter, and 
food, is able to create for himself an artificial climate where- 
ever he chose s to reside. The power to resist cold consists 
chiefly in preventing the heat which is generated by the 
vital processes of the body from being lost by radiation. 
Warm clothing, such as we wear in winter, has, in reality, 
the same temperature as that which is worn in summer ; 
but, by reason of being thick and porous, it is a bad con- 
ductor of heat, and thus prevents the escape of that 
produced by the body. If woollen fabrics were intrinsically 
warm, no one would wrap a piece of flannel, or blanket, 
around a block of ice to prevent its melting in summer. 

49. The faculty of generating heat explains how it is 
that we are enabled to resist the effects of cold; but how 
does the body withstand a temperature higher than its 



47. State what is said respecting the temperature of the human body. 

48 ^ Ability of man to adapt himself to different climates ? In what does the 
power to resist cold consist ? What is said about warm clothing ? 

49. Men in an atmosphere above the boiling-point ? In. foundries and glass 
works ? 



RESPIRATION. 145 

own ? Men have been known to remain several minutes in 
an atmosphere heated above the boiling-point of water, and 
yet the temperature of their own bodies was not greatly ele- 
vated. Those who labor in foundries and glass-works are 
habitually subjected to very high degrees of temperature, 
but they do not suffer in health more than those engaged 
in many other occupations. 

50. The regulation of the temperature of the body is 
effected by means of perspiration, and by its evaporation. 
So long as the skin acts freely and the air freely absorbs 
the moisture, the heat of the body does not increase, for 
whenever evaporation takes place, it is attended by the 
abstraction of heat — that is, the part becomes relatively 
colder. This may be tested by moistening some part of 
the surface with cologne, ether, or other volatile liquid, 
and then causing it to evaporate rapidly by fanning. The 
principle that evaporation produces cold has been in- 
geniously and practically employed, in the manufacture 
of ice, by means of freezing machines. 

51. Spontaneous Combustion. — Is it possible that 
the temperature of the living body can be so increased, 
that its tissues will burn spontaneously ? From time to 
time, cases have been reported in which, by some mysteri- 
ous means, considerable portions of the human body have 
been consumed, apparently by fire, the victim being found 
dead, or incapable of explaining the occurrence. Hence, 
the theory has been current that, under certain condi- 
tions, the tissues of the body might become self-ignited ; 
and the fact that this so-called spontaneous combustion 
has ordinarily taken place in those who had been addicted 
to the use of alcoholic drinks, has given a color of proba- 
bility to the opinion. It has been supposed that the flesh 
of these unfortunate persons becoming saturated with the 
inflammable properties of the alcohol thus taken into the 

50. The regulation of the temperature of the body. Give the explanation. 

51, 52. State what is said of spontaneous combustion. 

1 



146 RESPIRATION. 



system, took fire upon being exposed to a flame, as of a 
lighted candle, or, indeed, without any external cause. But, 
whether this be possible or not, one thing is certain, this 
strange kind of combustion has never been actually wit- 
nessed by any one competent to give a satisfactory account 
of it. 

52. The results that have been observed may be satis- 
factorily explained by the accidental ignition of the clothes, 
or other articles near the body, and by the supposition 
that the individual was at the time too much stupefied by 
intoxication, to notice the source of danger, and provide 
for his safety. The highest temperature that has been 
observed in the body, about 112° Fahrenheit, is too low 
to ignite the vapor of alcohol; much less will it cause 
the burning of animal tissues. It is undoubtedly true 
that when the tissues are filled with alcohol, combus- 
tion will more easily take place than when the body is in 
a normal state ; but, under any condition, the combustion 
of the body requires a higher degree of heat than can be 
generated by the body itself, or the mere proximity of a 
lighted candle, or any cause of a similar character. 



REVIEW QUESTIONS. 147 



QUESTIONS FOR TOPICAL REVIEW. 

PAGE 

1. What is the object of respiration ? 123 

2. What are the special organs of respiration ? 123 

3. In what organs do js a change in the blood take place ? 123 

4. What is the nature of the change ? 123, 133 

5. Where are the lungs situated, and what is the character of the sub- 

stance of which they are composed ? 123, 125 

6. Describe the facilities provided for the lung movements 124 

7. Describe the trachea, or windpipe 124, 125, 127, 128 

8. Describe the bronchial tubes, and their uses 125, 126 

9. What can you state in relation to the epiglottis ? 126, 127 

10. What are the cilia and what use do they probably serve ? 128 

11. How may the lungs be affected by not being properly protected ? 128 

12. Describe the movements necessary to the act of perfect respiration. . . 128, 129 

13. What is the diaphragm, and what is its office ? 128, 129 

14. How may the organs of respiration be so improved as to increase their 

capacity and power ? 129, 37 

15. What is stated in relation to the frequency of respiration ? 129, 130 

16. To what extent may the act of respiration be subjected to our wills ? 130 

17. What may be said to be the capacity of the lungs ? 130, 131 

18. How long does it take every particle of air in the lungs to be expelled and 

new air to take its place ? 130 

19. What would be the consequences, if the entire capacity of the lungs 

were constantly used ? 130, 131 

20. What would be the consequences to a fish put into water from which the 

air had been completely exhausted ? Why ? 131 

21. What is the air, and what are its parts ? 131, 136, 138 

22. What is the character of the air that has been just breathed ? 132 

23. Why is it that such air is not fit for respiration ? 132, 139 

24. What are the effects, as recorded in notable cases, of confinement in places 

the air of which has been breathed " over and over ?" 133 

25. What can you state of changes in the blood from respiration ? 133 

26. What of the air, as an article of food ? 133, 134 

27. What, on the subject of interchange of gases in the lungs ? 134 

28. Explain the difference between arterial and venous blood 134, 135 

29. Explain, if you can, the cau?e of the difference 135 

30. State what you can in relation to blue blood 135, 

31. In relation to the amount of labor exerted in respiration 135, 136 

32. In relation to the deleterious properties of different gases 136, 137 

33. In relation to the dust that floats in the air 137, 138 

34. What are the properties of carbonic acid gas ? 132, 138, 141 

35. In what places is carbonic acid gas commonly found ? 132, 138, 139 

36. Describe the effects of carbonic acid gas 132, 128, 139, 141 

37. What are the general effects of breathing any impure atmosphere ? . . . . 139, 140 

38. What are Nature's provisions for purifying the air ? 141, 142 

39. What hints and directions are given on the subject of ventilation ? . . . . 142, 143 

40. How does the temperature of the body compare with the medium in which 

it lives ? H3 

41. How is temperature of the body regulated and sustained ? 143, 144, 145 

42. State what you can on the subject of spontaneous combustion 145, 146 



148 THE NERVOUS SYSTEM. 



chapter ix. 

The Nervous System. 

Animal and Vegetative Functions — Sensation, Motion, and Volition — 
The Structure of the Nervous System — TJie White and Gray Sub- 
stances — The Brain — Its Convolutions — TJie Cerebellum — The Spi- 
nal Cord and its System of Nerves — TJie Anterior and Posterior 
Boots— The Sympathetic System of Nerves— TJie Properties of Nerv- 
ous Tissue — Excitability of Nervous Tissues — Tlie Functions of the 
Spinal Nerves and Cord — TJie Direction of the Fibres of the Cord — 
Reflex Activity, and its Uses — TJie Functions of the Medulla Oblon- 
gata and the Cranial Ganglia — Tlie Reflex Action of the Brain. 

1. Animal Functions. — The vital processes which we 
have been considering, in the three previous chapters, of 
digestion, circulation, and respiration — belong to the class 
of functions known as vegetative functions. That is, they 
are common to vegetables as well as animals; for the 
plant, like the animal, can originate nothing, not even 
the smallest particle of matter; and yet it grows, blossoms, 
and bears fruit, by reason of obtaining and digesting the 
nutriment which the air and soil provide. The plant has 
its circulatory fluid and channels, by which the nutriment 
is distributed to all its parts. It has, also, a curious ap- 
paratus in its foliage, by which it abstracts from the air 
those gaseous elements so necessary to its support; and 
thus it accomplishes vegetable respiration. These vege- 
tative functions have their beginning and end within the 
organism of the plant; and their object is the preservation 
of the plant itself, as well as of the entire species. 

2. The animal, in addition to these vegetative functions, 
has another set of powers, by the use of w r hich he becomes 
conscious of a world external to himself, and brings him- 

1. W T hat processes are known as the vegetative functions? Why so called? 
What properties and functions does the plant possess ? Their object ? 

2. What second set of powers has the animal ? What functions are mentioned ? 
The advantage they give ? 



THE NERVOUS SYSTEM. 149 



self into active relations with it. By means of the vege- 
tative processes, his life and species are maintained; while, 
by means of certain animal functions, he feels, acts, and 
thinks. These functions, among which are sensation, 
motion, and volition, not only distinguish the animal from 
the plant, but, in proportion to their development, elevate 
one creature above another ; and it is by virtue of his pre- 
eminent endowment, in these respects, that man holds his 
position at the head of the animal creation. 

3. Among animals whose structure is very simple, the 
hydra, or fresh-water polyp, being an example, no special 
organs are empowered to perform separate functions ; but 
every part is endowed alike, so that if the animal be cut 
into pieces, each portion has all the properties of the entire 
original; and, if the circumstances be favorable, each of 
the pieces will soon become a complete hydra. As we ap- 
proach man, in the scale of beings, we find that the organs 
multiply, and the functions become more complete. The 
function of motion, the instruments of which — the muscles 
and bones — have been considered in former chapters, and 
all the other animal functions of man, depend upon the set 
of organs known as the nervous system. 

4. The Nervous System. — The intimate structure 
of this system differs from any tissue which we have be- 
fore examined. It is composed of a soft, pulpy substance, 
which, early in life, is almost fluid, but which gradually 
hardens with the growth of the body. When examined 
under the microscope, it is found to be composed of two 
distinct elements : — (1) the white substance, composing 
the larger proportion of the nervous organs of the body, 
which is formed of delicate cylindrical filaments, about 
■g-^Vo °f an i ncn i 11 diameter, termed the nerve-fibres ; and 
(2) the gray substance, composed of grayish-red, or ashen- 

3. Animals whose structure is simple? As we approach man? Dependence 
of the animal functions of man ? 

4. The nervous tissues, of what composed ? When examined hy the aid of the 
microscope ? The white substance ? The gray substance ? 



150 THE NERVOUS SYSTEM. 

colored cells, of various sizes, generally possessing one or 
more off-shoots, which are continuous with the nerve- 
fibres just mentioned. 

5. The gray, cellular substance constitutes the larger 
portion of those important masses, which bear the name of 
nervous centres and ganglia (from ganglion, a knot), and 
in which all the nerve-fibres unite. These white nerve- 
fibres are found combined together in long and dense 
cords, called nerves (from neuron, a cord), which serve to 
connect the nervous centres with each other, and to place 
them in communication with all the other parts of the 
body which have sensibility or power of motion. That 
part of the nervous system which is concerned in the ani- 
mal functions, comprises the brain, the spinal cord, and the 
nerves which are derived therefrom; these are, together, 
called the cerebrospinal system (Fig. 40) ; while that other 
set of organs, which presides over, and regulates the vege- 
tative functions, is called the sympathetic system of nerves. 

6. The Brain. — The brain is the great volume of nerv- 
ous tissue that is lodged within the skull. It is the largest 
and most complex of the nervous centres, its weight, in the 
adult, being about fifty ounces, or one-fortieth of that of 
the whole body. The shape of the brain is oval, or egg- 
shaped, with one extremity larger than the other, which is 
placed posteriorly in the skull, to the concavity of which it 
very closely conforms. The brain consists chiefly of two 
parts; the cerebrum, or brain proper, and the cerebellum, 
or "little brain." In addition to these, there are several 
smaller organs at the base, among which is the commence- 
ment or expansion of the spinal cord, termed the medulla 
oblongata, or oblong marrow. 

7. The tissue of the brain is soft and easily altered in 

5. Nervous centres and ganglia? Nerves? What do they serve? Cerebro- 
spinal system ? 

6. Location of the brain ? Its weight ? Its shape ? Of what it cousists ? What 
oryans at the base ? 

7. The tissue of the brain ? What, therefore, is required ? Blows on the head ? 
Membranes of the brain ? Blood sent to the brain ? 



THE XERVOUS SYSTEM. 151 




Fig. 40.— The Cerebro-Spinal System. 



152 THE NERVOUS SYSTEM. 

shape by pressure; it therefore requires to be placed in a 
well-protected position, such as is afforded by the skull, or 
cranium, which is strong without being cumbrous. In 
the course of an ordinary lifetime, this bony box sustains 
many blows, with little inconvenience; while, if they fell 
directly upon the brain, they would at once, and com- 
pletely, disorganize that structure. Within the skull, the 
brain is enveloped by certain membranes, which at once 
protect it from friction, and furnish it with a supply of 
nutrient vessels; they are called the arachnoid, or "spider's 
web," the dura mater and the pia mater, or the "tough" 
and "delicate coverings." The supply of blood sent to 
the brain is very liberal, amounting to one-fifth of all 
that the entire body possesses. The brain of man is 
heavier than that of any other animal, except the ele- 
phant and whale. 

8. The Cerebrum. — The brain proper, or cerebrum, is 
the largest of the intracranial organs, and occupies the en- 
tire upper and front portion of the skull. It is almost com- 
pletely bisected, by a fissure, or cleft, running through it 
lengthwise, into two equal parts called hemispheres. The 
exterior of these hemispheres is gray in color, consisting 
chiefly of nerve-cells, arranged so as to form a layer of gray 
matter one-fifth of an inch in thickness, and is abundantly 
supplied with blood-vessels. The interior of the brain, 
however, is composed almost wholly of white substance, or 
nerve-fibres. 

9. The surface of the cerebrum is divided by a consid- 
erable number of tortuous and irregular furrows, about 
an inch deep/ into " convolutions," as shown in Fig. 41. 
Into these furrows the gray matter of the surface is ex- 
tended, and, in this manner, its quantity is vastly in- 
creased. The extent of the entire surface of the brain, 

8. Size of the brain proper ? How divided? The exterior of the hemispheres ? 
The interior ? 

9. The surface of the cerebrum, how marked ? The gray matter of the surface ? 
Extent of the entire brain surface ? Source of nervous power ? What further ? 



THE NERVOUS SYSTEM. 



153 



with the convolutions unfolded, is computed to be equal to 
four square feet ; and yet it is easily enclosed within the 
narrow limits of the 
skull. When it is 
stated that the gray 
matter is the true 
source of nervous 
power, it becomes 
evident that this 
arrangement has an 
important bearing 
on the mental ca- 
pacity of the indi- 
vidual. And it is 
noticed that in 
children, before the 
mind is brought 
into vigorous use, 
these markings or 
furrows on the sur- 
face are compara- 
tively shallow and 




Fig. 41.— Upper Surface of the Cerebrum. 
, Longitudinal Fissure. 



igitu 
B, The Hemispheres. 

indistinct; the same fact is true of the brain in the less 
civilized races of mankind and in the lower animals. It is 
also noticeable, that among animals, those are the most 
capable of being educated which have the best develop- 
ment of the cerebrum. 

10. The Cerebellum. — The "little brain" is placed 
beneath the posterior part of the cerebrum, and, like the 
latter, is divided into hemispheres. Like it, also, the sur- 
face of the cerebellum is composed of gray matter, and its 
interior is chiefly white matter. It has, however, no con- 
volutions, but is subdivided by many crescentic, parallel 
ridges, which, sending down gray matter deeply into the 



10. Location of the "little brain ?" 
Its subdivisions ? Its size ? 



How divided ? Its surface and interior ? 



154 



THE NERVOUS SYSTEM. 



white, central portion, gives the latter a somewhat branched 
appearance. This peculiar appearance has been called 



.;■-"'" ""'" ~ "~ ""'■:-— .. 




Fig. 42.— Vertical Section of the Brain. 



A, Left Hemisphere of Cerebrum. 

B, Corpus Callosum. 

C, Optic Thalamus. 



D, The Pons Varolii. 

E, Upper extremity of the Spinal Cord. 

F, The Arbor Vitae. 



the arbor vitce, or the "tree of life," from the fact that 
when a section of the organ is made, it bears some resem- 
blance to the trunk and branches of a tree (Fig. 42, F). 
In size, this cerebellum, or "little brain/' is less than one- 
eighth of the cerebrum. 

11. From the under surface of the cerebrum, and from 
the front margin of the cerebellum, fibres collect together 
to form the medulla oblongata (Fig. 43, MA), which, on is- 
suing from the skull, enters the spinal column, and then 
becomes known as the spinal cord. From the base of the 
brain, and from the sides of the medulla originate, also, 
the cranial nerves, of which there are twelve pairs. These 
nerves are round cords of glistening white appearance, and, 

11. Medulla oblongata ? Cranial nerves ? Their shape and position ? 






THE XERVOUS SYSTEM. 



155 



like the arteries, generally lie remote from the surface of 
the body, and are well protected from injury. 




Fig. 43.— The Base of the Brain. 

12. The Spinal Cord. — The spinal cord, or " marrow/' 
is a cylindrical mass of soft nervous tissue, which occupies 
a chamber, or tunnel, fashioned for it in the spinal column 
(Fig. 44). It is composed of the same substances as the 
brain ; but the arrangement is exactly reversed, the white 
matter encompassing or surrounding the gray matter in- 
stead of being encompassed by it. The amount of the 
white substance is also greatly in excess of the other ma- 
terial. A vertical fissure partly separates the cord into 
two lateral halves, and -each half is composed of two sep- 
arate bundles of fibres, which are named the anterior and 
posterior columns. 

13. These columns have entirely different uses, and each 



12. The spinal cord? Of what composed ? How divided? Each half ? 

13. Uses of these columns? Importance of this part of the nervous system? 
How protected ? 




THE NERVOUS SYSTEM. 



of them unites with a different 
portion of the nerves which have 
their origin in the spinal cord. 
The importance of this part of 
the nervous system is apparent 
from the extreme care taken to 
protect it from external injury. 
For, while a very slight disturb- 
ance of its structure suffices to 
disarm it of its power, yet so 
staunch is its bony enclosure, 
that only by very severe injuries 
is it put in peril. The three 
membranes that cover the brain 
are continued downward so as 
to envelope and still further 
shield this delicate organism. 

14. The Spinal Nerves.— 
The spinal nerves, thirty- one 
pairs in number, spring from 
each side of the cord by two 
roots, an anterior and a poste- 
rior root, which have the same 
functions as the columns bear- 
ing similar names. The poste- 
rior root is distinguished by pos- 
sessing a ganglion of gray mat- 
ter, and by a somewhat larger 
size. The successive points of 
departure, or the off-shooting of 
these nerves, occur at short and 
nearly regular intervals along 
the course of the spinal cord. 
Soon after leaving these points, 



., Cerebrum. 
, Cerebellum, 
i, D, Spinal Cord. 



14. The spinal nerves? The posterior root! 
Their office ? 



The nerves, how arranged? 



THE NERVOUS SYSTEM. 157 



the anterior and posterior roots unite to form the trunk 
of a nerve, which is distributed, by means of branches, 
to the various organs of that part of the body which this 
nerve is designed to serve. The spinal nerves supply 
chiefly the muscles of the trunk and limbs and the ex- 
ternal surface of the body. 

15. The tissue composing the nerves is entirely of the 
white variety, or, in other words, the nerve-fibres; the 
same as we have observed forming a part of the brain. 
But the nerves, instead of being soft and pulpy, as in the 
case of the brain, are dense in structure, being hardened 
and strengthened by means of a fibrous tissue which sur- 
rounds each of these delicate fibres, and binds them to- 
gether in glistening, silvery bundles. Delicate and mi- 
nutely fine as are these nerve-fibres, it is probable that 
each of them pursues an unbroken, isolated course, from its 
origin, in the brain or elsewhere, to that particular point 
which it is intended to serve. For, although their extrem- 
ities are often only a hair's breadth distant from each other, 
the impression which any one of them communicates is 
perfectly distinct, and is referred to the exact point whence 
it came. 

16. This may be illustrated in a simple manner, thus : 
if two fingers be pressed closely together, and the point of a 
pin be carried lightly across from one to the other, the eyes 
may be closed, and yet we can easily note the precise instant 
when the pin passes from one finger to the other. If the 
nerve-fibres were less independent, and if it were necessary 
that they should blend with and support each other, all 
accuracy of perception would be lost, and all information 
thus afforded would be pointless and confused. These sil- 
very threads must, therefore, be spun out with an infinite 
degree of nicety. Imagine, for instance, the fibre which 



15. The nerve tissue? Its character ? Course of each nerve fibre ? 

16. How may we illustrate the fact? The fibre connecting the brain with a 
point in the foot ? 



158 THE NERVOUS SYSTEM. 

connects the brain with some point on the foot, — its length 
cannot be less than one hundred thousand times greater 
than its diameter ; and yet it performs its work with as 
much precision as fibres that are comparatively much 
stronger and less exposed. 

17. The Sympathetic System. — The sympathetic 
system of nerves remains to be described. It consists of a 
double chain of ganglia, situated on each side of the 
spinal column, and extending through the cavities of the 
trunk, and along the neck into the head. These ganglia 
are made up for the most part of small collections of gray 
nerve-cells, and are the nerve-centres of this system. 
Prom these, numerous small nerves are derived, which 
connect the ganglia together, send out branches to the 
cranial and spinal nerves, and form networks in the vicin- 
ity of the stomach and other large organs. A considerable 
portion of them also follows the distribution of the large 
and small blood-vessels, in which the muscular tunic ap- 
pears. Branches also ascend into the head, and supply 
the muscles of the eye and ear, and other organs of sense. 

18. In this manner, the various regions of the body are 
associated with each other by a nervous apparatus, which 
is only indirectly connected with the brain and spinal 
cord; and thus it is arranged that the most widely sep- 
arated organs of the body are brought into close and 
active sympathy with each other, so that, " if one member 
suffers, all the other members suffer with it." From this 
fact, the name sympathetic system, or the great sympathetic 
nerve, has been given to the complicated apparatus we have 
briefly described. Blushing and pallor are caused by men- 
tal emotions, as modesty and fear, which produce opposite 
conditions of the capillaries of the face by means of these 
sympathetic nerves. 



17. The sympathetic system of nerves ? Of what does it consist ? 

18. Association of the various regions of the body ? If one member suffers ? 
Blushing ? 



THE NERVOUS SYSTEM. 159 

19. The Properties of Nervous Tissue. — We have 
seen that in all parts of this system, there are only two 
forms of nervous tissue ; namely, the gray substance and 
the white substance, so called from their difference of color 
as seen by the naked eye; or the nerve-cell, and the nerve- 
fibre, so called from their microscopic appearance. Now 
these two tissues are not commonly mingled together, but 
either form separate organs, or distinct parts of the same 
organs. This leads us to the conclusion that their respec- 
tive uses are distinct. And this proves to be the simple 
fact; wherever we find the gray substance, we must look 
upon it as performing an active part in the system, that is, 
it originates nervous impulses ; the white matter, on the 
contrary, is a passive agent, and serves merely as a con- 
ductor of nervous influences. Accordingly, the nervous 
centres, composed so largely of the gray cells, are the great 
centres of power, and the white fibres are simply the in- 
struments by which the former communicate with the near 
and distant regions of the body under their control. 

20. We may compare the brain, then, to the capitol, or 
seat of government, while the various ganglia, including 
the gray matter of the cord, like so many subordinate 
official posts, are invested with authority over the outly- 
ing provinces ; and the nerves, with the white matter of 
the cord, are the highways over which messages go and 
return between these provinces and the local or central 
governments. But both forms of nervous tissue possess 
the same vital property, called excitability ; by which term 
is meant, that when a nerve-cell or fibre is stimulated by 
some external agent, it is capable of receiving an impres- 
sion and of being by it excited into activity. A ray of 
light, for example, falling upon one extremity of a fibre 
in the eye, excites it throughout its whole length ; and its 

1 9. Properties of nervous tissue ? Office of the gray substance ? Of the white ? 
The nervous centres ? White fibres ? 

20. What comparison is made between the brain and the nation's capitol? 
The vital property, excitability ? What example is given ? 



160 THE NERVOUS SYSTEM. 

other extremity, within the brain, communicating with a 
nerve-cell, the latter, in its turn, is excited, and the sensa- 
tion of sight is produced. 

21. What sort of change takes place in the nervous 
tissue when its excitability is aroused, is not known; 
certainly none is visible. On this account, it has been 
thought by some, that the nerve-fibre acts after the man- 
ner of a telegraph wire : that is, it transmits its messages 
without undergoing any material change of form. But, 
though the comparison is a convenient one, it is far from 
being strictly applicable ; and the notion that nerve-force 
is identical with electricity has been fully proved to be 
incorrect. 

22. The Functions of the Nerves. — The nerves 
are the instruments of the two grand functions of the 
nervous system, Sensation and Motion. They are not the 
true centres of either function, but they are the conductors 
of influences which occasion both. If the nerve in a limb 
of a living animal be laid bare, and irritated by pinching, 
galvanizing, or the like, two results follow, namely: the 
animal experiences a sensation, that of pain, in the part to 
which the nerve is distributed, and the limb is thrown into 
convulsive action. When a nerve in a human body is cut 
by accident, or destroyed by disease, the part in which it 
ramifies loses both sensation and power of motion ; or, in 
other words, it is paralyzed. We accordingly say that the 
nerves have a twofold use, a sensory and motor function. 

23. If a nerve that has been exposed be divided, and the 
inner end, or that still in connection with the nerve-cen- 
tres, be irritated, sensation is produced, but no movement 
takes place. But if the outer end, or that still connected 
with the limb, be irritated, then no pain is felt, but mus- 



21 . Change in the nervous tissues ? Nerve force and electricity ? 

22. Functions of the nerves ? In the case of the nerve of a living animal ? Of 
the human body ? 

23. If an exposed nerve be divided ? What is proved ? The course of the sensory 
set of fibres ? Of the motor set ? To what are they likened ? 



THE NERVOUS SYSTEM. 161 

cular contractions are produced. Thus we prove that there 
are two distinct sets of fibres in the nerves ; one of which, 
the sensory fibres, conduct toward the brain, and another, 
the motor fibres, conduct to the muscles. The former may 
be said to begin in the skin and other organs, and end in 
the brain ; while the latter begin in the nervous centres 
and end in the muscles. They are like a double line of 
telegraph wires, one for inquiries, the other for responses. 

24. We have already spoken of the two roots of the spinal 
nerves, called from their points of origin in the spinal 
cord, the anterior and posterior roots. These have been 
separately cut and irritated in the living animal, and it has 
been found that the posterior root contains only sensory 
fibres, and the anterior root has only motor fibres. So that 
the nerves of a limb may be injured in such a way that it 
will retain power of motion and yet lose sensation ; or the 
reverse condition, feeling without motion, may exist. Be- 
tween these two sorts of fibres, no difference of structure 
can be found ; and where they have joined to form a nerve 
it is impossible to distinguish one sort from the other. 

25. Occasionally a nerve is so compressed as to be tem- 
porarily unable to perform its functions : a transient par- 
alysis then takes place. This is the case when the leg or 
arm "gets asleep," as it is expressed. When such is the 
condition with the leg, and the person suddenly attempts 
to walk, he is liable to fall, inasmuch as the motor fibres 
cannot convey orders to the muscles of the limb. Another 
fact is observed : there is no sensation in this nerve at the 
point of its compression ; but the whole limb is numb, and 
tingling sensations are felt in the foot, the point from 
which the sensory fibres arise. 

26. This illustrates the manner in which the brain in- 

24. The two roots of the spinal nerves ? What has been found ? Difference 
of the two sorts of fibres ? Result of their union ? 

25. Transient paralysis ? When such is the case with the leg? 'What other 
fact is observed ? 

26. What does this illustrate ? Sensation ? The feeling after a limb has been 
amputated ? Striking of the " funny bone ?" 



162 THE NERVOUS SYSTEM. 

terprets all injuries of the trunk of a nerve. Sensation or 
pain is not felt at the point of injury, but is referred to the 
outer extremities of the nerye, where impressions are habit- 
ually received. This is the reason why, after a limb has 
been amputated by the surgeon, the patient appears to 
suffer pain in the member that has been severed from the 
body; while some form of irritation at the end of the nerve 
in the wound, or stump, is the real source of his distress. 
Again, when the "funny-bone" — that is, the ulnar nerve 
at the elbow, — is accidentally struck, the tingling sensa- 
tions thus produced are referred to the outer side of the 
hand and the little finger, the parts to which that nerve is 
distributed. 

27. All the spinal nerves, and two from the brain, are 
concerned in both sensation and motion. Of the remainder 
of the cranial nerves, some are exclusively motor, others 
exclusively sensory; and still others convey, not ordinary 
sensations, but special impressions, such as sight, hearing, 
and smell, which we have yet to consider. However much 
the functions of the nerves seem to vary, there is but little 
difference discoverable in the nerves themselves, when ex- 
amined under the microscope. Whatever difference exists 
must be accounted for in consequence of the nerves com- 
municating with different portions of the gray matter of 
the brain. The rate of motion of a message, to or from 
the brain along a nerve, has been measured by experi- 
ment upon the lower animals, and estimated in the case of 
man at about two hundred feet per second. As compared 
with that of electricity, this is a very slow rate, but, in 
respect to the size of the human body, it is practically in- 
stantaneous. 

28. The Functions of the Spinal Cord. — As the 



27. The spinal nerves, and two from the brain ? Of the remainder ? Difference 
in the nerves ? How accounted for ? The rate of conduction along a nerve ? As 
compared with electricity ? 

28. Functions of the anterior and posterior columns of the cord ? If the cord 
be divided ? 



THE NERVOUS SYSTEM. 163 

anterior and posterior roots of the spinal nerves have sepa- 
rate functions, so the anterior and posterior columns of 
the cord are distinct in function. The former are con- 
cerned in the production of motion, the latter in sensation. 
If the cord be divided, as before in the case of the nerve, it 
is found that the parts below the point of injury are de- 
prived of sensation and of the power of voluntary motion 
on both sides of the body, a form of paralysis which is 
called paraplegia. 

29. This form of disease, paraplegia, is sometimes seen 
among men, generally as the result of a fall, or some other 
severe accident, by which the bones of the spine are broken, 
and the cord is crushed, or pierced by fragments of bone. 
The parts which are supplied by nerves from the cord 
above the point of injury are as sensitive and mobile as 
before. The results are similar, whether the division hap- 
pens at a higher or lower portion of the spinal cord ; but 
the danger to life increases proportionally as the injury 
approaches the brain. When it occurs in the neck, the 
muscles of inspiration are paralyzed, since they are sup- 
plied by nerves issuing from that region ; and as a result 
of this paralysis, the lungs are unable to act, and life is 
speedily brought to a close. 

30. When the spinal cord of an animal has been cut, in 
experiment, it may be irritated in a manner similar to that 
alluded to when considering the nerves. If, then, the 
upper cut surface be excited, it is found that pain, refer- 
able to the parts below the cut, is produced ; but when the 
lower cut surface is irritated, no feeling is manifested. So 
we conclude that in respect to sensation, the spinal cord is 
not its true centre, but that it is merely a conductor, and 
is therefore the great sensory nerve of the body. When 
the lower surface of the cut is irritated, the muscles of the 

29. Paraplegia ? Result and danger to life ? When the injury occurs in the 
neck? 

30. Experiment of cutting the spinal cord of an animal ? What inference is 
drawn? 



164 THE NERVOUS SYSTEM. 

parts below the section are violently contracted. Hence, 
we conclude that, in respect to the movements ordered by 
the will, the spinal cord is not their source ; but that it 
acts only as a conductor, and is, accordingly, the great 
motor nerve of the body. 

31. Direction of the Fibres of the Cord. — If one 
lateral half of the spinal cord be cut, or injured, a very sin- 
gular fact is observed. All voluntary power over the mus- 
cles of the corresponding half of the body is lost, but the 
sensibility of that side remains undiminished. This result 
seems to show that the motor fibres of the cord pursue a 
direct course, while its sensory fibres are bent from their 
course. And this has been proved to be the fact; for im- 
mediately after the posterior roots — the conductors of sen- 
sory impressions — join the posterior columns, they enter 
the gray matter of the cord, and passing over, ascend to the 
brain on the opposite side. Accordingly, the sensory fibres 
from the right and left sides interlace each other in the 
gray matter ; this arrangement has been termed the decus- 
sation, or crossing of these fibres. This condition serves 
to explain how a disease or injury of the cord may cause a 
paralysis of motion in one leg, and a loss of sensation in 
the other. 

32. The direction of the anterior, or motor columns of 
the cord, is downward from the brain. In the cord itself, 
the course of the motor fibres is for the most part, a direct 
one ; but in the medulla oblongata, or upper extremity of 
the cord, and therefore early in their career, these fibres 
decussate, or cross from side to side in a mass ; and not 
separately, as in the case of the posterior fibres just men- 
tioned. This arrangement is termed the decussation of 
the anterior columns of the medulla. 

33. From this double interlacing of fibres results a 

3 1 . What singular fact is noticed ? What does the result show ? 

32. Direction of the anterior or motor columns? In the cord itself? In the 
medulla oblongata ? The decussation ? 

33. Result of the double interlacing of fibres? Where is the seat of pain. 



THE NERVOUS SYSTEM. 165 

crossed action between the original and terminal extremity 
of all nerve-fibres which pass through the medulla ; 
namely, those of all the spinal nerves. Consequently, if 
the right hand be hurt, the left side of the brain feels the 
pain ; and if the left foot move, it is the right hemisphere 
which dictates its movement. For the same reason, when 
a loss of sensation and power of motion affecting the right 
side of the body alone is observed, the physiologist under- 
stands that the brain has been invaded by disease upon its 
left side. This affection is termed hemiplegia, or the " half- 
stroke." The full-stroke, which often follows the rupture 
of a blood-vessel in the brain, is commonly call paralysis. 

34. The Reflex Action of the Cord.— We have 
already considered the cord as the great motor and sensory 
neive of the body, but it has another and extremely impor- 
tant use. By virtue of the gray matter, which occupies 
its central portion, it plays the part of an independent 
nerve centre. The spinal cord not only conducts some 
impressions to the brain, but it also arrests others; and, as 
it is expressed, " reflects" them into movements by its own 
power. This mode of nervous activity is denominated the 
Reflex Action of the cord. 

35. A familiar example of this power of the cord is 
found in the violent movements which agitate a fowl 
after its head has been cut off. The cold-blooded animals 
also exhibit reflex movements in an astonishing degree. 
A decapitated centipede will run rapidly forward, and will 
seemingly strive to overturn, or else climb over obstacles 
placed in its way. A frog similarly mutilated will sustain 
its headless body upon its feet, in the standing posture, 
just as it might do if it were still alive. If pushed over, 
it will regain its feet ; and if the feet are irritated, it will 

when the right hand is hurt ? The moving of the foot ? Loss of sensation in one 
tide of the body ? 

34. What other important use has the cord? What is the activity denomi- 
nated ? 

3 5 . Example of the fowl ? Centipede ? Frog ? What do they prove ? 



166 THE NERVOUS SYSTEM. 

jump forward. There can be no doubt that, in the lower 
animals, movements may take place which are completely 
divorced from the will, sensation, and consciousness; for 
in those animals, as well as in man, these faculties have 
their principal seat within the brain. 

36. An irritation is necessary, in most instances, to 
awaken reflex movements. In the case of the decapitated 
fowl, its muscles are excited to convulsive action by 
reason of its being thrown upon the hard ground and 
roughly handled. Let it be treated differently, and the 
convulsions will not take place : let it be laid gently upon 
soft cotton, and the body will remain comparatively quiet. 
It may comfort some people to know that the convulsions 
which follow decapitation are not attended with pain ; nor 
are they a necessary part of the " act of death," as some 
suppose. 

37. In the human body, likewise, actions are excited 
that are entirely distinct from the ordinary voluntary 
efforts. It is not permissible, desirable, nor even necessary 
to decapitate a man that the body may be disconnected 
from his brain, in order to test the effect of irritation upon 
the spinal cord; although the bodies of beheaded crimi- 
nals have been experimented upon, and caused to move by 
powerful galvanic batteries. The resort to such means of 
experiment is rendered unnecessary by the occurrence of 
certain deplorable cases of disease and injury, which effect- 
ually sever all communication between the brain and a 
large part of the body. 

38. Thus, the cord may be so far injured, as the result 
of accident, as to terminate all sensation and voluntary 
motion in the lower half of the body, the patient seem- 
ingly becoming lifeless and powerless from the waist down- 
ward. And yet, by tickling or pinching either foot, the leg 

36. What is necessary in most cases to awaken reflex movements? In the 
case of the fowl ? Convulsions which follow decapitation ? 

37. Actions in the human body distinct from voluntary efforts? 

38. Reflex action after injury of the cord ? Why not due to the muscles ? 



THE NEEVOTJS SYSTEM. 167 

of the same side may be made to jerk, or even to kick with 
considerable force ; but, unless the patient is observing his 
limbs, he is wholly unconscious of these movements, which 
are, therefore, performed independently of the brain. And 
they are in nowise due to the muscles of the limb; for, 
if the cord itself becomes diseased below the point of in- 
jury, the muscles cease to contract. 

39. For the production of this form of nervous action 
three things are requisite — (1) a nerve to conduct messa- 
ges from the surface of the body, one of that variety for- 
merly described as sensory, but which are now incapable of 
awakening sensation ; (2) a portion of uninjured spinal 
cord which shall reflect or convert impressions into im- 
pulses ; and (3) a motor nerve to conduct impulses outward 
to the muscles. The power of the cord to enforce reflex 
acts resides in the gray matter, into which the reflex nerves 
enter and from which they depart, by means of their pos- 
terior and anterior roots respectively. 

40. The Uses of the Reflex Action.— The reflex 
activity of the cord is exhibited in the healthy body in 
many ways, but since it is never accompanied with sensa- 
tion, we do not readily recognize it in our own bodies. 
Reflex movements are best studied in the cases of other 
persons, when the conditions enable us to distinguish 
between acts that are consciously, and those that are un- 
consciously performed. For example, if the foot of a per- 
son soundly asleep be tickled or pinched, it will be quickly 
withdrawn from the irritation. 

41. Similar movements may be observed in cases where 
the consciousness and sensation are temporarily obliter- 
ated by disease, or by means of narcotic poisons. If the 
arm of a person who has been rendered insensible by 



39. What are the requisites for the production of this form of nervous action? 

40. Why do we not readily recognize the reflex activity of the cord in our own 
bodies ? How best studied in others ? Example ? 

41 . Similar movements ? Arm of a person ? Melted wax or heated coin on the 
hand ? 



168 THE KERVOUS SYSTEM. 

chloroform, be raised, and then allowed to fall, it will be 
noticed that the limb does not drop instantly, like a life- 
less member, but a certain amount of rigidity remains in 
its muscles, which resists or breaks the force of its descent. 
Again, when a substance like melted sealing-wax, or a 
heated coin, falls upon the hand, the limb is snatched 
away at once, even before the feeling of pain has been 
recognized by the brain. When jolted in a rapidly moving 
car, we involuntarily step forward or backward, so as to 
preserve the centre of gravity of the body. 

42. These and similar acts are executed by the same 
mechanism as that previously described in the case of 
paralysis from an injury of the spinal cord. The muscles 
thus called into play, are those which are ordinarily under 
the sway of the will, but which in these cases act through 
this reflex action of the cord, altogether independently of 
the will. A healthful reflex activity produces an elasticity, 
or " tone," of the voluntary muscular system, which, in a 
great measure, explains the existence in the young and 
vigorous of a feeling of buoyancy and reserve power. Its 
possessor is restlessly active, and it may appropriately be 
said of him, " he rejoiceth as a strong man to run a race." 
But this reflex energy may be deficient. This is true when 
the blood is poor and wanting in its solid ingredients, or 
the circulation is feeble ; the muscles, then, are flabby and 
weak, and the person himself is said to be " nerveless," or 
indisposed to exertion. Shivering from cold, and trem- 
bling from fear, may, in part, be referred to a temporary 
loss of tone, resulting from a powerful impression upon the 
brain. 

43. An excess of this activity may also be observed in 
disease. In this condition, the excitability of the cord is 
unnaturally aroused, and frequent and violent movements 

42. Result of healthful reflex activity ? When may the reflex energy be defi- 
cient ? 

43. Excess of this activity in disease ? Hydrophobia, etc. ? The difference In 
severity of the convulsions ? 



THE NEKVOUS SYSTEM. 169 

of the limbs and body, called convulsions, are the result. 
The convulsions of young children, and the nervous agita- 
tion of chorea, or St. Vitus' s dance, are reflex in character ; 
as are also the symptoms attending poisoning by strychnine, 
and those terrible diseases, tetanus, or " locked jaw," and 
hydropliobia. The severity of the convulsions is not the 
same in all cases of these disorders ; but, in those last men- 
tioned the most violent spasmodic movements are provoked 
by the slightest form of irritation — such as the sound of 
pouring water, the sight of any glittering object, the glanc- 
ing of a mirror, the contact of cool air, or even the touch 
of the bedclothes. 

44. Another variety of reflex motions takes place in cer- 
tain involuntary muscles, and over these the cord exercises 
supreme control. They are principally those movements 
which aid the performance of digestion and nutrition, the 
valve-action of the pylorus, and other movements of the 
stomach and intestines. In these movements the mind 
shares no part. And it is well that this is so ; for since 
the mind is largely occupied with affairs external to the 
body, it acts irregularly, becomes fatigued, and needs fre- 
quent rest. The spinal cord, on the contrary, is well fitted 
for the form of work on which depends the growth and 
support of the body, as it acts uniformly, and with a ma- 
chine-like regularity. 

45. These operations are not accompanied by conscious- 
ness ; for, as a general rule, the attention is only called to 
them when they become disordered. Many a person does 
not know where his stomach is situated, until he discovers 
its position by reason of a feeling of distress within it, 
produced by giving that organ improper work to perform. 
In this manner the higher and nobler faculties of the 
mind are liberated from the simply routine duties of the 



44. Another variety of reflex motions ? What are they? What is stated of the 
mind in connection with these movements ? 

45. Consciousness in these operations? Physical wants ? 



170 THE tfEKVOUS SYSTEM. 

body ; and we are thus left to direct the attention, the rea- 
son, and the will to the accomplishment of the great ends 
of our existence. If it were otherwise, we could only find 
time to attend to our ordinary physical wants. 

46. The objects of the reflex activity of the cord are 
threefold. In the first place, it acts as the protector of man, 
in his unconscious moments. It is his unseen guardian, 
always ready to act, never growing weary, and never re- 
quiring sleep. Nor does its faithful action wholly cease 
with the cessation of life in other parts. In the second 
place, it is the regulator of numerous involuntary motions 
that are necessary to the nutrition of the body. Here its 
actions are entirely independent of the brain, and are per- 
formed in a secret and automatic manner. And, thirdly, it 
acts as a substitute, and regulates involuntary movements 
in the muscles usually under the influence of the will. It 
thus takes the place of the higher faculties in performing 
habitual acts, and permits them to extend their operations 
more and more beyond the body and its material wants. 

47. The Functions of the Medulla Oblongata. 
— The prolongation of the spinal cord, within the skull, 
has been previously spoken of as the medulla oblongata. 
It resembles the cord, in being composed of both white 
and gray matter, and in conducting sensory and motor in- 
fluences. It likewise gives rise to certain nerves, which are 
here called cranial nerves (from cranium, the skull). All 
except two of these important nerves spring from the me- 
dulla, or the parts immediately adjoining it ; the exceptions 
are the two nerves taking part in the special senses of sight 
and smell, which nerves have their origin at the base of 
the cerebrum. 

48. The decussation, or crossing of the motor columns, 
has been previously described, when treating of the direc- 

46. How many objects may the reflex activity be said to have ? State the first. 
The second. The third. 

47. How does the medulla oblongata resemble the cord ? 

48. What final fact is observed in the crossing of the motor columns? 



THE NERVOUS SYSTEM. 171 

tion of the nerve-fibres of the cord ; and the singular fact 
has been alluded to, that when one side of the brain is 
injured, its effects are limited to the opposite side of the 
body. One more fact remains to be observed in this con- 
nection, namely, this crossed action does not usually take 
place in the cranial nerves. Accordingly, when apoplexy, 
or the rupture of a blood-vessel, occurs in the right hemi- 
sphere of the cerebrum, the left side of the body is paralyzed, 
but the right side of the face is affected ; this is because 
that part of the body is supplied by the cranial nerves. 

49. A portion of the medulla presides over the impor- 
tant function of respiration, and from it arises the pneu- 
mogastric nerve, so called because its branches serve both 
the lungs and stomach. The feelings of hunger, thirst, 
and the desire for air are aroused by means of this nerve. 
The wounding of the gray matter of the medulla, even of 
a small portion of it, near the origin of the pneumogastric 
nerve, at once stops the action of the lungs and causes 
death. In consequence of the importance of this part, it 
has been termed the " vital knot." We find, also, that its 
location within the skull is exceedingly well protected, it 
being quite beyond the reach of any ordinary form of 
harm from without. 

50. The Functions of the Cranial Ganglia. — The 
uses of the smaller gray masses lying at the basv. of the 
brain are not well ascertained; and, on account of their 
position, so remote from the surface, it would, at first, seem 
well-nigh impossible to study them. But, from the results 
following diseases in these parts, and from experiments 
upon inferior animals, they are becoming gradually better 
understood; and there is reason to believe that eventually 
the physiological office of each part will be clearly ascer- 
tained and defined. It is believed, however, but not abso- 



50. The uses of the smaller gray masses at the base of the brain ? 



172 THE NERVOUS SYSTEM. 

lutely proven, that the anterior masses, like the anterior 
roots of the spinal nerves and the anterior columns of 
the cord, are concerned in the production of motion; in 
fact, that they are the central organs of that function. 
The posterior gray masses are, on the contrary, supposed 
to be the seat of sensation. 

51. The Function of the Cerebellum. — The func- 
tion of the cerebellum, or " little brain," is the direction 
of the movements of the voluntary muscles. When this 
organ is the seat of disease or injury, it is usually observed 
that the person is unable to execute orderly and regular 
acts, but moves in a confused manner as if in a state of 
intoxication. Like the larger brain, or cerebrum, it 
appears to be devoid of feeling; but it takes no part in 
the operations of the mind. 

52. The Function of the Cerebrum. — The cere- 
brum, or brain proper, is the seat of the mind; or, speak- 
ing more exactly, it is the material instrument by which 
the mind acts ; and, as it occupies the highest position in 
the body, so it fulfils the loftiest uses. All the other 
organs are subordinate to it : the senses are its messengers, 
which bring it information from the outer world, and the 
organs of motion are its servants, which execute its com- 
mands. Here, as in the nervous apparatus of lower grade 
already considered, the gray matter is the element of 
power; and, in proportion as this substance increases in 
extent, and in proportion to the number of convolutions 
in the hemispheres, do the mental faculties expand. 

53. There have been a few, but only a few, men of dis- 
tinguished ability whose brains have been comparatively 
small in size ; the rule being that great men possess large 
brains. The relative weight of the brain of man, as com- 



5 1 . Function of the cerebellum ? When it is diseased ? 

52. Where is the seat of the mind? The subordination of the other organs? 
The gray matter ? 

53. What is stated of men in connection with the size of their brain ? With 
the brains of other animals ? 



THE NERVOUS SYSTEM. 173 

pared with the weight of the body, does not, in all instan- 
ces, exceed that of the inferior animals ; the canary and 
other singing-birds have a greater relative amount of nerv- 
ous matter than man ; but man surpasses all other crea- 
tures in the size of the hemispheres of the cerebrum, and 
in the amount of gray substance which they contain. 

54. It is a singular fact that this cerebral substance is 
insensitive, and may be cut without causing pain. The 
removal of a considerable quantity of the brain has taken 
place, as the result of accident, without causing death, and 
without even affecting seriously the intellect. A remark- 
able case of injury of the brain is recordedj in which, 
from the accidental explosion of gunpowder used in blast- 
ing a rock, the " tamping-iron" was driven directly through 
the skull of a man. This iron rod, three feet and seven 
inches long, an inch and a quarter in diameter, and weigh- 
ing more than thirteen pounds, entered the head below the 
ear and passed out at the top of the skull, carrying with it 
portions of the brain and fragments of bone. The man 
sustained the loss of sight on one side, but otherwise 
recovered his health and the use of his faculties. More- 
over, disease has occurred, compromising a large portion 
of the brain, without impairing the faculties of the mind, 
when the disease was limited to one side only. 

55. Impressions conveyed to the hemispheres from the 
external world arouse the mental operations called 
thought, emotion, and the will. These are the god- 
like attributes which enable man to subjugate a world, 
and afterward cause him to " sigh for other worlds to con- 
quer;" which enable him to acquaint himself with the 
properties of planets millions of miles distant from him, 
and which give him that creative power by which he 
builds and peoples the new worlds of poetry and art. 



54. Sensitiveness of the brain substance? The removal of a portion of the 
brain ? State the remarkable case mentioned ? 

55. Thought, emotion, and will ? What power do they give us ? 



174 THE NERVOUS SYSTEM. 

56. All these mental acts, and many others, are devel- 
oped through the action of the brain ; not that the brain 
and the mind are the same, or that the brain secretes 
memory, imagination, or the ideas of truth and justice, as 
the stomach secretes the gastric juice. But rather, as the 
nerve of the eye, stimulated by the subtile waves of light, 
occasions the notion of color, so the brain, called into 
action by the mysterious influences of the immaterial soul, 
gives rise to all the intellectual, emotional, and voluntary 
activities of mankind. 

57. The cerebrum, according to our present knowledge 
of it, must- be regarded as a single organ, which produces 
different results, according as it is acted upon by the im- 
material mind in different ways. Eecent investigations, 
however, seem to prove that the faculty of language is de- 
pendent upon a small part of the left hemisphere of the 
cerebrum, near the temple. At least, in almost every 
instance where this part is diseased, the patient can no 
longer express himself in speech and writing. 

58. The Reflex Action of the Brain.— The reflex 
function of the organs within the skull is very active and 
important. Like that of the cord, it protects the body by 
involuntary movements, it regulates the so-called vegeta- 
tive acts, and it takes the place of the will in controlling 
the voluntary muscles, when the attention is turned in 
other directions. The reflex power of the medulla governs 
the acts of respiration, which are absolutely and continu- 
ously essential to life. Respiration is, as we have seen, 
partly under the influence of the will; but this is due in 
part to the fact that respiration is indirectly concerned in 
one of the animal functions, that of speech. 

59. Reflex action also occasions coughing and sneezing, 



56. Are the brain and the mind identical ? 

57. What do we know of the cerebrum and its powers ? 

58. The reflex function of the organs within the skull ? The reflex power of 
the medulla ? Respiration ? 

59. What else does reflex action occasion ? Winking? Other examples ? 



THE NERVOUS SYSTEM. 175 

whenever improper substances enter the air-passages. 
Winking is an act of the same sort, and serves both to 
shield the eyes from too great glare of light, and to pre- 
serve them by keeping the cornea moist. Looking at the 
sun or other strong light, causes sneezing by reflex action. 
Laughing, whether caused by tickling the feet or by some 
happy thought, and also sobbing, are reflex acts, taking- 
place by means of the respiratory muscles. 

60. Certain of the protective reflex movements call into 
play a large number of muscles, as in the balancing of the 
body when walking along a narrow ledge, or on a slippery 
pavement. The dodging motion of the recruit, when the 
first cannon ball passes over his head, is reflex and invol- 
untary. The fact that these involuntary, reflex acts are 
performed with great precision, will explain why it is that 
accidents seldom befall the somnambulist, or sleep-walker, 
although he often ventures in most perilous places. 

61. Walking, sitting, and other acts of daily life, be- 
come automatic, or reflex, from habit : the mind is seldom 
directed to them, but delegates their control to the medulla 
and spinal cord. Thus a person in walking, may traverse 
several miles while absorbed in thought, or in argument 
with a companion, and yet be conscious of scarcely one in 
a thousand of the acts that have been necessary to carry 
his body from one point to another. By this admirable 
and beautiful provision, the mind is released from the 
charge of the ordinary mechanical acts of life, and may 
devote itself to the exercise of its nobler faculties. And it 
is worthy of notice, the greater the use of these faculties, 
the more work does the reflex function assume and per- 
form; and thus the employment of one insures the im- 
provement of the other. 



60. Muscles called into play by certain reflex movements ? The somnambulist ? 

61. What is said of walking and other acts in connection with the office per- 
formed by the medulla and spinal cord ? 



176 REVIEW QUESTIONS. 



QUESTIONS FOR TOPICAL REVIEW. 

PAGE 

1. State fully what is meant by the term vegetable function 148 

2. To what is man indebted for his position as the head of the animal crea- 

tion ? 148, 149 

3. What can you state on the subject of special organs for separate functions ? 149 

4. Describe, as fully as you can, the structure of the nervous system 149, 150 

5. Describe the brain, its location, size, shape, and structure 150, 152 

6. Describe the brain proper, or cerebrum 152, 153, 174 

7. What connection is noticed between the cerebrum and mental 

power ? 153, 172, 174 

8. Describe the little brain, or cerebellum 153, 154, 172 

9. Describe the spinal cord 154, 155, 156 

10. What are the spinal nerves, and how are they arranged ? 156, 157 

11. What is the character and substance of their tissues ? 157 

12. State how the nerve-fibres perform their office, and give the illustra- 

tion 157, 158 

13. Describe the sympathetic system of nerves 158 

14. State what is meant by the properties of nervous tissue, and give the 

illustration 159, 160 

15. Explain what is meant by the functions of the nerves, and give the 

illustration 160, 161, 162 

16. What is meant by a transient paralysis of a nerve ? Give the illustra- 

tion 161, 162 

17. What can you state of the rate of message-motion along a nerve ? 162 

18. What are the functions of the spinal cord ? 162, 163, 164, 165 

19. State what you can of the form of paralysis known as paraplegia 163 

20. What experiments, with results, upon the spinal cord are noted? 163, 164 

21. Explain how injury of the cord may produce paralysis of motion in one 

leg, and at the same time a loss of sensation in the other 164 

22. Explain how, if the right hand be hurt, the left side of the brain is made to 

feel the pain 165 

23. Now, explain as fully as you can the direction of the fibres of the cord. 164, 365 

24. What is understood by the reflex action of the cord ? 165 

25. Wbat experiments are mentioned to prove this power of the cord ? 165, 166 

26. What are the uses of the reflex action of the cord ? 167-170 

27. What illustrations are mentioned to show such uses ? 167-170 

28. What is the medulla oblongata ? 154, 170 

29. What are the functions of the medulla oblongata ? 170, 171 

30. What can you state of the functions of the cranial ganglia ? 171, 172 

31. What are the functions of the cerebellum ? 172 

32. What is the function of the cerebrum ? 172, 174 

33. In what way does the size of tne brain generally indicate the character 

of the man ? 172, 173 

34. What facts show that the gray substance of the brain is insensitive ? 173 

35. Upon what does the faculty of language seem to depend ? 174 

36. What has been observed in support of this statement ? 174 

37. Of what importance is the reflex action of the brain ? 174, 175 

38. In what ways is this importance made manifest ? 174, 175 



THE SPECIAL SENSES. 177 



chapter x. 

The Special Senses. 

The Production of Sensations — Variety of Sensations — General Sensi- 
bility — Pain and its Function — Special Sensation, Touch, Taste, 
Smell, Sight, and Searing — The Hand, the Organ of Touch — The 
Sense of Touch — Delicacy of Touch — Sensation of Temperature and 
Weight — The Tongue the Organ of Taste — The Nerves of Taste — 
The Sense of Taste and its Relations with the other Senses — The 
Influence of Education on the Taste — The Nasal Cavities, or the 
organs of Smell — TJie Olfactory Nerve — The Uses of the Sense of 
Smell — The Sense of Rearing and Sound — The Ear, or the organ 
of Rearing — The External, Middle, and Internal Ear — The Sense 
of Sight — Light — The Optic Nerve — The Eyeball and its Coverings — 
The Function of the Iris — The Sclerotic, Choroid, and Retina — The 
Tears and their Function — The Movements of the Eyeball — The 
Function of Accommodation. 

1. Production of Sensations. — We have already 
seen that the true centre of sensation is some organ within 
the skull, probably among the gray masses at the base of 
the brain; but the mind never perceives impressions at 
that point ; but, on the contrary, always refers them to the 
external organs of sensation. Hence, it is convenient to 
say, that those outer parts possess the property of sensibil- 
ity. For instance, we say that we hear with the ear, taste 
with the tongue, and feel with the fingers. That this is 
not the exact truth is proven by the fact, that whenever 
the nerve connecting one of these organs with the brain is 
severed, it at once loses its capacity for sensation. 

2. Consciousness, another faculty of the brain, is neces- 
sary to complete a sensation. During sleep, and in other 
unconscious states, the usual impressions are presented to 



1 . True centre of sensation ? Place of the mind's impressions ? What is it 
convenient to say ? What further is stated ? 

2. Consciousness ? During sleep ? In profound insensibility ? 

8* 



178 THE SPECIAL SEKSES. 

the ear, the nose, and the skin, but they fail to excite sen- 
sations, because the nerve-centres are inactive. In pro- 
found insensibility, from chloroform or ether, a limb may 
be removed without occasioning the least feeling. 

3. Variety of Sensations. — All animals have some 
degree of sensibility. It is of course feeble and indistinct 
in the lower forms of life, but increases in power and vari- 
ety as we ascend the scale. In the earth-worm, the nerv- 
ous system is very simple, the sensibility being moderate 
and alike in all parts : hence, if its body be cut into two 
pieces, each piece will have the same degree of feeling as 
before. As we approach man, however, the sensations 
multiply and become more acute; the organs are more 
complex, and special parts are endowed with special gifts. 
These special organs cannot be separated from the rest of 
the body without the loss of the functions they are de- 
signed to exercise. 

4. The lowest form of sensation, that of simple contact, 
is possessed by the lowest of the animal creation. The 
highest forms are those by which we are enabled to know 
the properties of external objects, such as shape, size, 
sound, and color. A variety of means of communicating 
with the outer world is the necessary possession of a high 
intelligence. Sensations are modified by use. They be- 
come more acute and powerful by moderate exercise ; or, 
they are dulled by undue excitement. The former is 
shown by the acute hearing of the Indian, by the sharp 
sight of the sailor, and by the delicate touch of the blind. 
The latter is exemplified by the impaired hearing of the 
boiler-maker, and the depraved taste of him who uses 
pungent condiments with his food. Again, impressions 
habitually presented may not be consciously felt; as is 
the case with the rumbling of carriages in a neighboring 



3. Sensibility in animals? In the earth-worm ? In man ? 

4. The lowest form of sensation? The highest? Sensations, how modified? 
What further can you state as to habitual impressions ? 



THE SPECIAL SENSES. 179 

street, or the regular ticking of a clock. All sensations 
become less vivid with the advance of age, especially hear- 
ing and vision. 

5. General Sensibility.— There is a property pos- 
sessed by nearly all parts of the human body which we 
call general sensibility. We have recently seen that the 
brain is wholly insensitive, and may be cut or pinched 
without pain. The same is true of the nails, hair, the 
scarf-skin or external covering of the body, and a few other 
structures. In these parts no nerves are found. On the 
other hand, the sensibility of the true skin, and of mucous 
membranes, as of the eye and nose, is exquisite, these or- 
gans having a large supply of sensory nerve-fibres. The 
bones and tendons have less of these fibres, and are only 
moderately sensitive. 

6. The sensibility of any part of the body, then, de- 
pends upon the number of nerves present; and, as a rule, 
the nervous supply is proportional to the importance of 
the part, and to its liability to injury. When, therefore, a 
surgical operation is performed, the most painful part of it 
is the incision through the skin ; the muscles, cartilage, 
and bone being comparatively without sensation. Hence, 
if we could benumb the surface, certain of the lesser oper- 
ations might be undergone without great inconvenience. 
This is, in fact, very successfully accomplished by means of 
the cold produced by throwing a spray of ether, or of some 
other rapidly evaporating liquid, upon the part to be cut. 

7. Tickling is a modification of general sensibility. At 
first, it excites a pleasurable sensation, but this soon passes 
into pain. It is only present in those parts where the 
sense of touch is feeble. But all impressions are not 
received from without: there are, also, certain internal 



5. General sensibility? What have we seen as regards the brain? O 
other structures is the same true ? 

6. The cause of sensibility ? Painful part in a surgical operation ? Be 
ing the surface ? How done by ether ? 

7. Tickling ? Internal sensations ? The nerves of general sensibility ? 



180 THE SPECIAL SENSES. 

sensations, as they are called, which depend upon the con- 
dition of the internal organs, such as appetite, hunger, 
thirst, the sense of satisfaction after taking food, dizziness 
when looking down from some lofty position, lassitude, 
drowsiness, fatigue, and other feelings of comfort or dis- 
comfort. General sensibility, whether of the internal or 
external organs of the body, chiefly depends upon the 
sensory fibres of the spinal nerve. The face, however, is 
supplied by the sensory cranial nerves. The sympathetic 
system has a low grade of feeling in health ; but disease in 
the parts served by it arouses an intense degree of pain. 

8. The Sensation of Pain. — What then is pain f Is 
it identical with ordinary sensibility ? There seems to be 
some necessary connection between the two feelings, for 
they take place through the same channels, and they are 
alike intense in the same situations. But sensibility 
habitually contributes to our sources of pleasure, the very 
opposite of pain; hence, these feelings cannot be identical. 

9. Pain must, therefore, be a modification of the general 
sensibility, which follows an excessive degree of excitement 
of the nerves ; there being a natural limit to the amount of 
stimulation which they will sustain. So long as this limit 
is observed, the part excited may be said to be simply sen- 
sitive; but when it is exceeded, the impression becomes 
painful. This difference between sensibility and pain is 
well shown by the effects of sunlight upon the eye. The 
indirect illumination of the sun arouses only the former 
feeling, and is indispensable to our comfort and existence ; 
while the direct ray received into the eye occasions great 
pain. 

10. The Uses of Pain. — The dread of pain is a valu- 
able monitor to the body. It puts us on our guard in the 
presence of danger; teaches moderation in the use of our 



8. Connection between pain and sensibility? 

9. Explain the difference between pain and sensibility. 

10t Dread of pain ? How may its value be appreciated ? Example. 



THE SPECIAL SEKSES. 181 

powers; indicates the approach of disease; and calls at- 
tention to it when present. The word disease, in fact, 
according to its original nse, had reference simply to the 
pain, or want of ease, which commonly attends disordered 
health. When we observe the serious mishaps which occur 
when sensibility and pain are absent, we cannot fail to 
appreciate its value. For example, a paralytic in taking a 
foot-bath, forgets to test its temperature, and putting his 
limbs into water while it is too hot, is severely scalded 
without knowing it. 

11. A traveller, overcome by cold and fatigue, lies down 
and falls asleep near a large fire, and when he is aroused in 
the morning, it is discovered that one of his feet has been 
insensibly destroyed. A grain of sand, lodging in an insen- 
sitive eye, may cause inflammation and even the loss of 
sight. If intense light were not painful to the eye, many 
a child would innocently gaze upon the glories of the sun 
to the ruin of his sight. 

12. Pain is, indeed, a present evil, but its relations with 
the future prove its mission merciful. Painful impressions 
cannot be recollected from past experience ; and they can- 
not be called into existence by the fancy. Considered in 
the light of results, pain has a use above that of pleasure ; 
for while the immoderate pursuit of the latter leads to 
harm, the tendency of pain is to restrict the hurtful courses 
of life, and in this manner to protect the body. 

13. The relations of pain to pleasure are thus described 
by the eminent physiologist, Magendie: — "By these sensa- 
tions Nature induces us to concur in the order which she 
has established among organized beings. Though it may 
appear like sophistry to say that pain is the shadow of 
pleasure, yet it is certain that those who have exhausted 
the ordinary sources of pleasure have recourse to the 



11. The case of the traveller? Grain of sand? The smn and child ? 

1 2. Mission of pain ? Painful impressions compared with those of pleasure t 

13. What does Magendie say of the relation of pain to pleasure ? 



182 THE SPECIAL SENSES. 

causes of pain, and gratify themselves by their effects. Do 
we not see in all large cities, that men who are debauched 
and depraved find agreeable sensations, where others ex- 
perience only intolerable pain ?" 

14. As to painful sensation among the inferior animals, 
the plan of Nature seems to be, that the higher the intel- 
ligence of the creature, and the more complete its power 
of defence, the more acute is its sensibility. We infer, 
therefore, that animals low in the scale of existence, and 
helpless, are not very liable to suffer pain. 

15. Special Sensation. — The sensations of simple 
contact and pain are felt by nearly all parts of the system, 
whether external or internal, and are the necessary con- 
sequence of the general sensibility ; but, so far as the ob- 
jects which surround us are concerned, these impressions 
are vague and passive in character, and inform the mind 
of none of the properties or powers of these objects. Be- 
sides these feelings, therefore, man is endowed with certain 
special sensations, which are positive and distinct in char- 
acter, and which he can call into exercise at will, and em- 
ploy in the pursuit of knowledge. For reasons relating to 
the original constitution of the body, these sensations are 
to be regarded as modifications of the general sensibility 
already alluded to, constructed with special reference to 
the different forces of Nature, of which we have any 
knowledge, such as heat, motion, gravity, sunlight, and 
the like. 

16. These distinct and active faculties are termed the 
special senses, and are five in number, viz., Touch, Taste, 
Smell, Sight, and Hearing. For the exercise of these 
senses, special organs are furnished, such as the hand, the 
tongue, the nose, the eye, and the ear. The manner in 
which the nerves of special sense terminate, varies in the 

14. The law of Nature as regards painful sensations among animals ? 

15. The sensation of contact and pain? Special sensations of man? How 
regarded ? 

1 6. What are the special senses ? Special organs for them ? 



THE SPECIAL SENSES. 183 

case of each organ, so that each is adapted to one set of 
sensations alone, and is incapable of perceiving any other. 
Thus the nerve of hearing is excited by the undulations of 
sound, and not by those of light, while the reverse is true 
of the nerve of sight; and the nerve of smell can appreciate 
neither of them, being capable only of taking cognizance 
of the odorous properties of bodies. 

17. By some writers six senses are accorded to man ; the 
additional one being either the sense of temperature, for as 
we shall presently see this is not the same as touch; or 
according to others, the muscular sense by which we are 
enabled to estimate the weights of bodies. The latter also 
differs in some respects from the sense of touch. 

18. Organs of Touch. — The sense of touch is pos- 
sessed by nearly all portions of the general surface of the 
body, but it finds its highest development in the hands. 
The human hand is properly regarded as the model organ 
of touch. The minute structure of the skin fits it admi- 
rably for this form of sensation : the cuticle, or scarf-skin, 
is fine and flexible, while the cutis, or true skin, contains 
multitudes of nerve-filaments, arranged in rows of papillm, 
or cone-like projections, about one-hundredth of an inch in 
length. It is estimated that there are 20,000 of these papillae 
in a square inch of the palmar surface of the hand. Now, 
although the nerves of the cutis are the instruments by 
which impressions are received and transmitted to the 
brain, yet the cuticle is essential to the sensation of touch. 
This is shown by the fact that whenever the true skin is 
laid bare, as by a burn or blister, the only feeling that it 
experiences from contact is one of pain, not that of 
touch. 

19. The office of the cuticle is thus made evident : it is 
to shield the nerve filaments from direct contact with ex- 



17. What is paid in relation to one more than the five senses ? 

18. The sense of touch, how prevalent ? What is said of the hand ? 

19. Office of the cuticle ? Tips of the fingers ? The fingers with thumb ? 



184 THE SPECIAL SENSES. 

ternal objects. At the tips of the fingers, where touch is 
most delicate, the skin rests upon a cushion of elastic 
material, and receives firmness and permanence of shape 
by means of the nail placed upon the less sensitive side. 
Besides these favorable conditions, the form of the arm is 
such, and its motions are so easy and varied, that we are 
able to apply the test of touch in a great number of direc- 
tions. The slender, tapering fingers, with their pliant 
joints, together with the strong opposable thumb, enable 
the hand to mold itself upon and grasp a great variety of 
objects ; so that great as are the delicacy and grace of the 
hand, it is not wanting in the elements of power. 

20. Its beauty and adaptation to the wants of man have 
made the hand an attractive theme for philosophers. 
They do not, however, always agree in their conclusions. 
One has the opinion that man has acquired his intelligence 
and achieved his place as " lord of creation," because he 
has this organ. Buffon, in effect, declares that with fingers 
twice as numerous and twice as long, we would become 
proportionally wiser; but Galen long ago took a more 
reasonable view, when he taught that "man is the wisest 
of animals, not because he possesses the hand; but because 
he is the wisest and understands its use, the hand has been 
given to him ; for his mind, not his hand has taught him 
the arts." Another has well said, that " no one can study 
carefully the human hand and fail to be convinced of the 
existence of the Deity." 

21. The Sense of Touch. — Touch is the simplest of 
the senses. It is that which the child first calls into ex- 
ercise in solving the early problems of existence ; and it is 
that which is in the most constant use throughout life. 
"We are brought by the touch into the most intimate rela- 
tions with external objects, and by it we learn the greater 
number, if not the most important, of the properties of 

20. What special importance is attributed to the hand ? 

21 . The simplicity of touch ? What does it teach us ? 



THE SPECIAL SENSES. 185 

these objects; such as size, figure, solidity, motion, and 
smoothness or roughness of surface. 

22. The sense of touch assists the other senses, especially 
that of sight, giving foundation and reality to their per- 
ceptions. Without it, the impressions received by the eye 
would be as vague aud unreal as the figures that float 
through our dreams. A boy who had been blind from 
birth, at the age of twelve years received sight by means 
of a surgical operation : at first, he was unable to distinguish 
between a globe and a circular card, of the same color, be- 
fore he had touched them. After that, he at once recog- 
nized the difference in their form. He knew the peculiari- 
ties of a dog and a cat by feeling, but not by sight, until 
one day, happening to take up the cat, he recognized the 
connection of the two sorts of impressions, those of touch 
and sight ; and then, putting the cat down, he said : " So, 
puss, I shall know you next time." 

23. Touch is considered the least liable to error of all 
the senses ; yet, if that part of the skin by which the sense 
is exercised is removed from its customary position, a false 




impression may be created in the mind. This is well il- 
lustrated by an experiment, which dates from the time of 
Aristotle. If we cross the middle finger behind the fore- 

22. Importance of the sense of touch to the development of the other senses ? 
23* Liability of touch to err? Describe the illustration. 



186 THE SPECIAL SENSES. 

finger, and then roll a marble, or some small object, upon 
the tips of the fingers (see Fig. 45), the impression will be 
that two marbles are felt. If the fingers, thus transposed, 
be applied to the end of the tongue, two tongues will be 
felt. When the nose is accidentally destroyed, the surgeon 
sometimes performs an operation for the purpose of form- 
ing a new one, by transplanting a partially removed piece 
of the skin of the forehead upon the injured part: then, if 
the new nose be touched or pinched, the feeling is referred 
to the forehead. This fact illustrates one important truth, 
that the nerves will re-unite after they have been cut, and 
feeling will be restored : if it were otherwise, a succession 
of slight cuts upon the fingers would seriously impair their 
tactile sensibility. 

24. The Delicacy of Touch. — Although the hand 
is the proper organ of this sense, yet it is exercised by 
various parts of the body, their degree of sensibility being 
proportional to the number of papillas they contain. The 
varying degrees of tactile delicacy of the different parts of 
the surface have been measured, in an ingenious manner, 
by means of a pair of compasses, tipped with small pieces 
of cork. The two points of the compasses are touched at 
the same moment to the skin, the eyes being closed, and it 
is found that, in sensitive parts, the distance between the 
points may be quite slight, and yet each be plainly felt; 
while, in less sensitive parts, the points of the compasses 
are felt as a single point, although they are separated one 
or two inches. 

25. At the tips of the fingers, the distance between the 
points being one-twentieth of an inch, a double impression 
is felt. The distance must be twice as great, for the palm ; 
four times as great, for the lips ; and, on the forehead, it 
must be twenty times greater. At the middle of the back, 
where the touch is least acute, the points must be sepa- 

24. The delicacy of touch ? Experiments with a pair of compasses ? 

25. Further experiments and results ? 



THE SPECIAL SENSES. 187 

rated more than two inches before they can be separately 
felt. Therefore, the sense of touch in the fingers is said to 
be fifty times more delicate than upon the posterior sur- 
face of the body. 

26. Exquisite delicacy of touch is attained by practice. 
This is shown in many of the lighter and more graceful 
employments of daily life. Without it, the skill of the 
painter, sculptor, and musician would be rude indeed. By 
training, also, the physician acquires the tactus eruditus, 
or discriminating touch ; but among the blind, delicacy of 
touch is most remarkable, and it here finds its highest 
value; for its possession, in a measure, compensates the 
loss of sight by enabling them to read, by means of raised 
letters, to work with certain tools, and even to play upon 
musical instruments. A person born without sight, and 
without hearing or voice, may, by the education of the 
touch, be rescued from apparent imbecility, and be taught 
not only to read and write, but even to perform household 
and other useful labors. 

27. Sensations of Temperature and Weight. — 
Each of these sensations has been described by the physi- 
ologists as a special sense, and they are rival candidates, so 
to speak, for the position and title of the sixth sense. In the 
sensation of temperature, or the ^hernial sense, touch bears 
a part, but the two feelings appear to be distinct. In proof 
of this, we observe, firstly, that they are not alike intense 
in the same situations; as, for example, the skin of the face 
and elbow, where the sense of touch is feeble, is very sensi- 
tive to impressions of heat and cold. Secondly, the ability 
to recognize temperature may be lost by paralysis, while 
the sensibility of touch remains unaffected. When the 
skin comes in contact with a very hot substance, the sen- 
sation felt is that of pain, not of touch. In like manner, a 



26. Exquisite delicacy of touch ? The same among the hlind? 

27. Rival candidates for the sixth sense? Give the two reasons on the sub- 
ject. 



188 THE SPECIAL SENSES. 

very cold substance causes pain, not the feeling of cold. 
So that a red-hot iron, and solid carbonic acid (the tem- 
perature of which is 108° below zero), feel alike; and each, 
if pressed slightly, will produce a blister. 

28. The muscular sense, by some considered distinct 
from touch, gives rise to the sensations of weight, and 
other forms of external resistance. That this feeling 
exists, is shown by the following simple experiment. If 
the hand be placed flat upon a table, and a somewhat 
heavy weight be put into it, touch alone is exercised 
and a feeling of pressure results; but if the hand be 
raised, a certain amount of muscular effort must be put 
forth, and thus the sensation of weight is recognized. 
Through the muscular sense, precision of effort is rendered 
possible ; for by it we learn to adjust the force exerted to 
the weight of the object to be lifted, moved, or carried. 
Without it, all our movements would necessarily become 
ill-regulated and spasmodic. In cases of disease, where the 
sensibility of the lower limbs is lost, while power of motion 
remains, the patient is able to stand erect so long as he 
can see his limbs ; but just as soon as his eyes are closed, 
he begins to waver, and will fall unless supported. 

29. The Organ of Taste.— The tongue is the special 
organ of the sense of taste ; but the back part of the mouth 
also possesses this faculty. The tongue is a muscular 
organ, the muscles composing it being so numerous and 
interwoven as to give it the freedom and variety of motion 
which it possesses. It can curve itself upward or down- 
ward ; it can extend or contract itself; and, with its point, 
can sweep the cavity of the mouth, in all directions, in 
the search for scattered particles of food. 

30. The upper surface of the tongue is peculiar, being 
marked by the presence of innumerable papillm, some of 

28. The muscular sense ? State what is said to illustrate the subject. 

29. The organ of taste ? The tongue ? Its powers of motion ? 

30. Peculiarities of the tongue ? Uses of the papillae ? 



THE SPECIAL SENSES. 189 

which are of microscopic size, resembling those that 
abound in the fingers, and in other parts of the body 
that have the sense of touch. Others are much larger, 
and give to the tongue its roughness of feeling and ap- 
pearance. Through the medium of these papillae, the 
tongue receives impressions of touch and temperature, as 
well as taste : indeed, its extremity is fully as delicate, in 
respect to tactile sensations, as the tips of the fingers them- 
selves. It can recognize the two points of the compasses 
when separated not more than one-twenty-fourth of an 
inch ; the back of it is much less sensitive to touch, while 
at the same time it is more highly sensitive to impressions 
of taste. 

31. Each lateral half of the tongue resembles the other 
in structure, and each receives the same number of nerves 
— three. One of these regulates motion, the other two are 
nerves of special sense. One of the latter supplies the 
front half of the tongue, and is called the gustatory nerve. 
This is a branch of the great cranial nerve, called the 
"fifth pair/' which ramifies in all parts of the face. The 
back of the tongue is endowed with the power of taste 
through a nerve known as the glosso-pharyngeal, because 
it is distributed both to the tongue and throat. This dif- 
ference in the nervous supply of the tongue becomes signif- 
icant, when we learn, as we shall presently, that each part 
of it perceives a different class of flavors. 

32. The Sense of Taste. — Taste is the special sense 
by means of which we discover the savors, or flavoring 
properties of the substances, which come in contact with 
the tongue. Mere contact with the surface of the tongue, 
however, is not sufficient, but contact with the extremities 
of the nerves of taste within the papillae is required. In 
order that the substance to be tasted may penetrate the 



31. Resemblance In the parte of the tongue? Powers and functions of the 
parts? 

32, Taste ? What are the requisites to taste ? 



190 THE SPECIAL SENSES. 

cells covering the nerves, it must either be liquid in form, 
or readily soluble in the watery secretion of the mouth, 
the saliva. The tongue must be moist also. If the sub- 
stance be insoluble, as glass or sand, or the tongue dry, the 
sense of taste is not awakened. In sickness, when the 
tongue is heavily coated, the taste is very defective, or, as 
is frequently expressed, " nothing tastes aright." 

33. All portions of the tongue are not alike endowed 
with the sense of taste, that function being limited to the 
posterior third, and to the margin and tip of this organ. 
The soft j>alate, also, possesses the sense of taste ; hence, 
an article that has an agreeable flavor may very properly 
be spoken of as palatable, as is often done. All parts of 
the tongue do not perceive equally well the same flavors. 
Thus, the front extremity and margin, which is the por- 
tion supplied by the " fifth pair" of nerves, perceives more 
acutely sweet and sour tastes ; but the base of the tongue, 
supplied by the glosso-pliaryngeal nerve, is especially sen- 
sitive to salt and bitter substances. The nerve of the front 
part of the tongue, as before stated, is in active sympathy 
with those of the face, while the relations of the other 
nerve are chiefly with the throat and stomach ; so that 
when an intensely sour taste is perceived, the countenance 
is involuntarily distorted, and is said to wear an acid ex- 
pression. On the other hand, a very bitter taste affects 
certain internal organs, and occasions a sensation of nau- 
sea, or sickness of the stomach. 

34. Relations of Taste with other Senses. — 
Taste is not a simple sense. Certain other sensations, as 
those of touch, temperature, smell, and pain, are blended 
and confused with it; and certain so-called tastes are really 
sensations of another kind. Thus an astringent taste, like 
that of alum, is more properly an astringent feeling, and 

33. Portion? of the tongue endowed with taste? Where else does the sense 
iodsre ? What is stated in respect to sweet and bitter flavors ? Reflex effects men- 
tioned ? 

34* What is stated of the relations of taste with other senses ? 



THE SPECIAL SENSES. 191 

results from an impression made upon the nerves of touch, 
that ramify in the tongue. Id like manner, the qualities 
known as smooth, oily, watery, and mealy tastes, are depend- 
ent upon these same nerves of touch. A burning or pungent 
taste is a sensation of pain, having its seat in the tongue and 
throat. A cooling taste, like that of mint, pertains to that 
modification of touch called the sense of temperature. 

35. Taste is largely dependent upon the sense of smell. 
A considerable number of substances, like vanilla, coffee, 
and garlic, which appear to possess a strong and distinct 
flavor, have in reality a powerful odor, but only a feeble 
taste. When the sense of smell is interfered with by hold- 
ing the nose, it becomes difficult to distinguish between sub- 
stances of this class. The same effect is frequently observed 
when smell is blunted during an ordinary cold in the head. 
Sight also contributes to taste. With the eyes closed, food 
appears comparatively insipid; and a person smoking 
tobacco in the dark is unable to determine by the taste 
whether his cigar is lighted or not. Accordingly, it is not 
a bad plan to close the nose and shut the eyes when about 
to swallow some disagreeable medicine. 

36. Influence of Education on the Taste. — The 
chief use of the sense of taste appears to be to act as a 
guide in the selection of proper food. Hence its organs are 
properly placed at the entrance of the digestive canal. As 
a general rule, those articles which gratify the taste are 
wholesome ; while the opposite is true of those which im- 
press it disagreeably. This statement is more exact in 
reference to the early years of life than to later years, 
when, by reason of mischievous habits, the sense of taste 
has become dulled or perverted. The desires of a child 
are simple ; he is fully satisfied with plain and wholesome 
articles of diet, and must usually "learn to like" those 



35. Its dependence on smell? on eight ? 

36. The chief use of the sense of taste ? The position of its organs ? The rule 
as regards wholesome and unwholesome food ? Remarks respecting the rule f 



l\)'Z THE SPECIAL SENSES. 

which have a strongly marked flavor. Accordingly, it is 
far easier at this age to encourage the preference for plain 
food, and thus establish healthful habits, than later in life 
to uproot habits of indulgence in stimulating substances, 
after their ill effects begin to manifest themselves. 

37. The tastes of men present the most singular diversi- 
ties, partly the result of necessity and partly of habit or 
education. The Esquimaux like the rank smell of whale 
oil, which is a kind of food admirably suited to the require- 
ments of their icy climate ; and travellers who go from our 
climate to theirs are not slow to develop a liking for the 
same articles that the natives themselves enjoy. The sense 
of taste is rendered very acute by education, as is shown in 
an especial manner by those who become professional 
" tasters" of tea and wine. 

38. The Sense of Smell— the Nasal Cavities. 
— The sense of smell is located in the delicate mucous 
membrane which lines the interior of the nose. That 
prominent feature of the face, the nose, which is merely 
the front boundary of the true nasal organ, is composed 
partly of bone and partly of cartilage. The upper part of 
it is united with the skull by means of a few small bones ; 
to which circumstance is due its permanence of shape. 
The lower portion, or tip cf the nose, contains several thin 
pieces of cartilage, which render it flexible and better able 
to resist the effects of blows and pressure. Behind the 
nose we find quite a spacious chamber, separated from 
the mouth by the hard palate, forming the "roof of the 
mouth," and by the soft palate (see Fig. 46) ; and divided 
into two cavities by a central partition running from be- 
fore backward. 

39. These nasal cavities, constituting the true beginning 
of the air-passages, extend from the nose backward to the 

37. Diversity in tastes of men ? How shown ? The education of the sense of 
taste ? 

38. Location of the sense of smell? The nose? " Roof of the mouth ?" 

39. Cavities of the nose ? Obstruction of the passage of air through them ? 



THE SPECIAL SENSES. 



193 



upper opening of the throat, and rise as high as the junc- 
tion of the nose with the forehead. The inner wall of 
each cavity is straight and smooth; but from the outer 
wall there jut into each cavity three small scroll-like 
bones. The structure of these bones is very light, and 
hence they have been called the " spongy" bones of the nose. 
In this manner, while the extent of surface is greatly in- 
creased by the formation of these winding passages, the 
cavities are rendered extremely narrow; so much so, in fact, 
that a moderate swelling of the mucous membrane which 
lines them, as from a cold, is sufficient to obstruct the pass- 
age of air through them. 

40. The Nerve of Smell. — The internal surface of 
the nasal passages is covered by a delicate and sensitive 
mucous membrane. Its surface is quite extensive, follow- 
ing as it does, all the inequalities produced by the curved 
spongy bones of the nose. The upper portion of it alone 
is the seat of smell, since that part alone receives branches 
from the " first pair" 
of cranial nerves, or 
the olfactory nerve, 
which is the special 
nerve of smell (see 
Fig. 43). In Fig. 46 
is shown the distri- 
bution of this nerve, 
in the form of an 
intricate network 
upon the two upper 
spongy bones. The 
nerve itself (1) does not issue, from the skull, but rests 
upon a thin bone which separates it from the cavity of the 
nose; and the branches which proceed from it pass through 
this bone by means of numerous small openings. The en- 




Fig. 46.— Section of the Right Nasal Cavity. 



40. The special nerve of smell ? Its location? 

9 



19± THE SPECIAL SENSES. 

graying represents the outer surface of the right nasal 
cavity ; the three wave-like inequalities, upon which the 
nervous network is spread out, are due to the spongy bones. 
The left cavity is supplied in the same manner. 

41. The nerves which ramify over the lower part of the 
membrane, and which endow it with sensibility to touch 
and pain, are branches of the " fifth pair" of nerves. An 
irritation applied to the parts where this nerve is distrib- 
uted occasions sneezing, that is, a spasmodic contraction 
of the diaphragm ; the object of which is the expulsion of 
the irritating cause. The manner in which the olfactory 
nerve-fibres terminate is peculiar. Unlike the extremities 
of other nerves, which are covered in by a greater or less 
thickness of tissue, these come directly to the surface of 
the mucous membrane, and thus come into very close con- 
tact with the odorous particles that are carried along by the 
respired air. The surface is at all times kept in a moist 
condition by an abundant flow of nasal mucus ; otherwise 
it would become dry, hard, and insensitive from the con- 
tinual passage of air to and fro in breathing. Birds, 
which respire more actively than men, have a special 
gland, for secreting a lubricating fluid, located in the air- 
passages of the head. 

42. The Uses of the Sense of Smell. — Smell is 
the special sense which enables us to appreciate odors. 
Touch, as we have seen, is largely concerned with solid 
bodies; and taste, with fluids, or with solids in solution. 
Smell, on the other hand, is designed to afford us informa- 
tion in reference to substances in a volatile or gaseous 
form. Invisible and subtile particles emanate from odor- 
ous bodies, and are brought by the respired air in contact 
with the terminal filaments of the olfactory nerve, upon 
which an agreeable or disagreeable impression is produced. 

4 1 . Branches of the " fifth pair" of nerves ? Nasal mucus ? Birds ? 

42. Smell ? Touch ? Taste ? Design of smell ? Invisible and gaseous parti- 
cles ? The extreme fineness of the particles ? Musk ? In other cases ? 



THE SPECIAL SENSES. 195 

The fineness of the particles that constitute odors is often so 
extreme, that they elude all attempts to measure or weigh 
them. A piece of musk, for instance, may be kept for sev- 
eral years, constantly emitting perfume, without any ap- 
preciable loss of weight. In other cases, a loss of substance 
is perceptible, such as the essential oils, which enter into 
the composition of the ordinary perfumes. 

43. Smell, like taste, aids us in the choice of proper 
food, leading us to reject such articles as have a rank or 
putrid odor, and which are, as a rule, unfit to be eaten. 
The highest usefulness of this sense, however, consists in 
the protection it affords to the organs of respiration. Sta- 
tioned at the gateways of the air-passages, it examines the 
current of air as it enters, and warns us of the presence of 
noxious gases, and of other and generally invisible ene- 
mies to health. Not all dangerous vapors are offensive, 
but almost all offensive vapors are unfit to be breathed. A 
number of small stiff hairs grow from the margin of 
the nostrils to prevent the entrance of dust and other at- 
mospheric impurities, which would be alike injurious to the 
olfactory mucous membrane and to the lungs. The benev- 
olent design of the Maker of our bodies may be observed in 
all parts of their mechanism ; but, probably, in none is it 
more clearly displayed than in connection with the sense 
of smell. 

44. The sense of smell is developed in a remarkable de- 
gree in certain of the inferior animals, and is especially 
acute in reference to the peculiar emanations that appear 
to characterize the different animals. The lion and other 
carnivorous beasts scent their prey from a great distance; 
and the fox-hound is able to track the fox through thickets 
and over open country for many miles; while the timid, 
helpless herbivora, such as the deer and sheep, find in the 



43. Aid given by smell? The highest use of the sense? Explain the manner. 

44. Sense of smell in the inferior animals ? How, and in what cases, illus- 
trated ? 



196 THE SPECIAL SENSES. 

sense of smell a means of protection against their natural 
enemies, of whose approach they are in this manner warned. 
By training this sense in the dog, and making it subservi- 
ent to his use, man is able to hunt with success certain shy 
and very fleet animals, which otherwise he could but sel- 
dom approach. Among men, individuals differ greatly in 
respect to the development of this sense; and especially 
in certain savage tribes it is found to be extremely deli- 
cate. Humboldt states that the natives of Peru can, by 
this sense, distinguish in the dark between persons of dif- 
ferent races. 

45. The Sense of Sight. — Sight, or Vision, is the 
special sense by means of which we appreciate the color, 
form, size, distance, and other physical properties of the 
objects of external nature. Primarily, this sense furnishes 
us with information concerning the different shades of 
color and the different degrees of brightness: these are 
the simple sensations of sight, such as the yellowness and 
glitter of a gold coin. In addition to these, there are com- 
posite visual sensations, produced by the joint action of 
the other senses and by the use of the memory and judg- 
ment; such as, in the case of the coin, its roundness, 
solidity, size, its distance and direction from us. So that 
many of our sensations, commonly considered as due to 
sight, are in reality the results of intellectual processes 
which take place instantaneously and unconsciously. 

46. This faculty not only has value in the practical 
every-day affairs of life, but it contributes so largely to the 
culture of the intellect and to our higher forms of pleasure, 
that some writers are disposed to rate it as the first and 
most valuable of the senses. Others, however, maintain 
that the sense of hearing does not yield in importance to 
that of sight; and they cite in support of their position 

45. What iB Right ? What information does it furnish ? Composite visual sen- 
sations ? 

46. Comparison between sight and hearing? Relative capacity of deaf and 
Wind? 






THE SPECIAL SENSES. 197 

the fact that the blind are commonly cheerful and gay, 
while the deaf are inclined to be morose and melancholy. 
In respect to -the relative capacity for receiving education 
in the deaf and blind, it is found that the former learn 
more quickly, but their attainments are not profound ; 
while the blind acquire more slowly, but are able to study 
more thoroughly. 

47. Light. — The Optic Nerve. — Unlike the senses 
previously considered — touch, taste, and smell — sight does 
not bring us into immediate contact with the bodies that 
are examined; but, by it, we perceive the existence and 
qualities of objects that are at a greater or less distance 
from us. In the case of the stars, the distance is incalcu- 
lable, while the book we read is removed but a few inches. 
Light is the agent which gives to this sense its wide range. 
The nature of this mysterious force is not known, and it is 
not here to be discussed; since its study belongs more 
properly to the province of natural philosophy. 

48. It is sufficient, in this connection, to state that the 
theory of light now generally accepted, and which best 
explains the facts of optics, is that known as the undula- 
tory theory. This theory supposes that there exists an 
intangible, elastic medium, which fills all space, and pene- 
trates all transparent substances, and which is thrown into 
exceedingly rapid undulations or waves, by the sun and 
every other luminous body ; the undulations being propa- 
gated with extreme rapidity, and moving not less than 
186,000 miles in a second. 

49. These waves are thought to produce in the eye the 
sensation of light, in the same manner as the sonorous 
vibrations of the air produce in the ear the sensation of 
.sound. That part of the eye which is sensitive to these 
waves is the expansion of the optic nerve. It is sensitive 



47. Sight, unlike the other senses ? In the case of the stars ? 

48. The undulatory theory of light? What does the theory suppose ? 

49. The sensation of light ? Optic nerve ? 



198 THE SPECIAL SENSES. 

to no other impression than that of light, and it is the only 
nerve which is acted upon by this agent. The optic nerve, 
also called the "second pair" of cranial nerves, is the means 
of communication between the eye and the brain. 

50. The two nerves constituting the pair, arise from 
ganglia lying at the base of the cerebrum, one of them on 
each side; from which points they advance to the eyes, 
being united together in the middle of their course in the 
form of the letter X (see Fig. 43). By this union the two 
eyes are enabled to act harmoniously, and in some respects 
to serve as a double organ. And by reason of this same in- 
timate nervous communication, when serious disease affects 
one eye, the fellow-eye is extremely liable to become the 
seat of symjmthetic inflammation; and this, if neglected, 
almost certainly results in hopeless blindness. 

51. The Organ of Sight. — The Eye. — The proximity 
of the eye to the brain, and the important part it per- 
forms in giving expression to the emotions, have given it 
the name of "the window of the soul." The exceeding 
beauty of its external parts, and the high value of its func- 
tion, have long made this organ the subject of enthusiastic 
study. It is chiefly within the last twenty years, however, 
that this study has been successful and fruitful of practical 
results. Several ingenious instruments have been invented 
for the examination of the eye in health and disease, and 
new operations have been devised for the relief of blindness 
and of impaired .vision. As a result, it is now a well- 
marked fact that, in civilized lands, the number of those 
who suffer from loss of sight is proportionally much less 
than in countries where science is less known and culti- 
vated. 

52. The most obvious fact in respect to the apparatus of 



50. The two nerves constituting the pair of nerves ? 

51. Why is the eye called the " window of the soul?" Why, the subject of 
enthusiastic study? 

52. The most obvious fact? The consequence? The next thing noticed? 
Jts range of view ? Of what does the organ of vision consist ? 



THE SPECIAL SENSES. 199 

sight is that there are two eyes, which may either act to- 
gether as one, and be fixed upon one object, or one eye may 
be used independently of the other. In consequence of 
this arrangement the loss of one eye does not necessitate 
blindness, and, in fact, it not infrequently happens that the 
sight of one eye may be long impaired or lost before the 
fact is discovered. We next notice that it is placed at the 
most elevated part of the body, in front, and near the brain. 
It also commands a wide range of view, being itself moved 
with great rapidity, and being further aided by the free 
motion of the head and neck. The organ of vision consists 
essentially of two parts : the optical instrument itself — the 
eyeball — and its enveloping parts, or the case in which the 
instrument is kept free from harm. The latter, which are 
external, and which we shall first consider, are chiefly the 
Orbits, the Eyelids, and the apparatus for the Tears. 

53. The Orbits. — The eyeball, which is a delicate 
organ, is well defended against external injury within the 
orbits or bony sockets of the head. These are deep conical 
hollows, bounded in part by the bones of the skull, and in 
part by those of the nose and cheek. The orbit juts out 
beyond the most exposed portion of the eyeball, as may be 
seen by laying a book over the eye, when it will be found 
that no part of the eyeball, unless it be very prominent, 
will be touched by the book ; so that the only direction in 
which an injury is liable to be received is immediately in 
front of the eye. The overhanging brow is itself covered 
by a layer of thick skin, studded with short, stout hairs, 
which are so bent as to prevent the perspiration from run- 
ning into the eye and obscuring vision. Through a hole 
in the bottom of the orbit, the nerve of sight passes out- 
ward from the brain. The orbit also contains a considera- 
ale amount of a fatty tissue, upon which, as upon an elastic 
cushion, the eye rests. 

53. The protection of the eyeball against injury? The overhanging brow? 
The opening for the optic nerve ? 



200 



THE SPECIAL SENSES. 




54. The Eyelids. — The eyelids are two movable cur- 
tains, or folds, which, when shut, cover the front part of 

the orbit, and hide the 
eye from view. The up- 
per lid is the larger, has a 
curved margin, and moves 
freely, while the lower lid 
is comparatively short 
and straight, and has but 
a slight degree of motion 
(Fig. 47). Skin covers 
the exterior of the lids, 
while a fine mucous 
membrane lines their in- 
ner surface, and is like- 
wise spread out over the 
entire front of the eye- 
ball. This membrane, 
which is called the Conjunctiva, is highly sensitive, and 
thus plays an important part in protecting the eye against 
the lodgment of sand, ashes, chaff, and other foreign parti- 
cles that are blown about in the air. This sensitive mem- 
brane will not endure the presence of these particles. If 
any find access, it causes a constant winking, a flow of 
tears, and other signs of irritation, until it is removed. 

55. The long, silky eyelashes, which garnish the edges 
of the lids, act like a sieve to prevent the entry of dust and 
the like; and together with the lids, they regulate the 
amount of light which is permitted to euter the eye, so that 
it is shielded from a sudden flood or glare of light. The little 
points seen in the figure just within the line of the lashes, 
especially on the lower lid, represent the mouths of numer- 
ous little sebaceous glands (Fig. 48, d,d), such as are always 



Fig. 47.— Front View of Right Eye. 
(Natural Size.) 

1. The Lachrymal, or tear gland, lying be- 
neath the upper eyelid. 

2. The Nasal Duct is shown by the dotted 
line. The * marks the orifice in the lower 
lid. 

The central black spot is the pupil; sur- 
rounding it is the iris ; and the triangular 
white spaces are the visible portion ot the 
sclerotic. 



54. What are the eyelids? The upper lid? The lower one? The mucous 
membrane of the eye ? 

55. The eyelashes ? The little points within the line of the lashes ? Of what 
nee are these glands ? 



THE SPECIAL SENSES. 201 

found in the neighborhood of hairs. These glands supply 
a thick, oily material which greases the edges of the lids 
and prevents their adhering together, and likewise prevents 
the overflow of the tears upon the cheek. 

56. The Lachrymal Fluid, or the Tears. — Just 
within the outer part of the bony arch of the brow, where 
the bone may be felt to be sharper than in other positions, 
is lodged a little organ called the lachrymal gland, the sit- 
uation of which is indicated in Fig. 47, 1. This is the 
gland whence flows the watery secretion, commonly called 
the tears, which is designed to perform an exceedingly im- 
portant duty in lubricating the lids, and in keeping the 
exposed surface of the eyeball moist and transparent. For, 
without this or some similar liquid, the front of the eye 
would speedily become dry and lustreless, like that of a 
fish which has been removed from the water : the simple 
exposure of the eye to the air would then suffice to. destroy 
vision. 

57. This secretion of the tears takes place at all times, 
during the night as well as the day; but it is seldom 
noticed, except when under the influence of some strong 
mental emotion, whether of sorrow or happiness, it is 
poured forth in excess, so as to overflow the lids. Strong 
light or a rapid breeze will, among many other causes, ex- 
cite the flow of the tears. That portion of this secretion 
which is not used in moistening the eye is carried off 
into the nose by a canal situated near the inner angle of 
the eye, called the nasal duct. This duct is shown in Fig. 
47, 2, and is connected with each lid by delicate tubes, 
which are indicated by dotted lines in the figure ; the as- 
terisk marks the little opening in the lower lid, by which 
the tears enter the nasal duct. By gently turning the 
inner part of that lid downward, and looking in a mirror, 

56. The location of the lachrymal gland ? The use of the gland ? 

57. When does the secretion of the tears occur? The secretion not used for 
the eye ? Location of the nasal duct ? Its use ? The overflow of tears in old 
people ? 

9* 



202 



THE SPECIAL SENSES. 



this small "lachrymal point" may be seen in your own 
eye. In old people, these points become everted, and do 
not conduct the tears to the nasal cavity, so that they are 
inconvenienced by an overflow of tears upon the face. 

58. Thus we observe that the gland which forms the 
tears is placed at the outer part of the eye, while their 
means of exit is at the inner angle of the eye ; which fact 
renders it necessary that this watery fluid shall pass over 
the surface of the eyeball before it can escape. This ar- 




Fig. 48.— Vertical Section of the Eye. (Enlarged.) 
C, The Cornea. 
A, The Aqueous Humor. 
I, The Iris. 
P, The Pupil. 
L, The Crystalline Lens. 



H, The Ligament of the Lens. 
B, The Ciliary Process. 
V, The Cavity containing the Vit- 
reous Humor. 
S, The Sclerotic. 



Ch, The Choroid. 

R, The Eetina. 

N. The Optic Nerve. 

DD, The Eyelids. 

X, The Levator Muscle of the Upper 

Lid. 
Y, The Upper Straight Muscle of the 

Eye. 
Z, The Lower Straight Muscle. 



rangement cannot be accidental, but evinces design, for it 
thus secures the perfect lubrication of the surface of the 
eye, and cleanses it from the smaller particles of dust 



Design of the arrangement ? 



THE SPECIAL SENSES. 203 

which may enter it, in spite of the vigilance of the lids 
and lashes. The act of winking, which is generally un- 
consciously performed, and which takes place six or more 
times in a minute, assists this passage of the tears across 
the eye, and is especially frequent when the secretion is 
most abundant. 

59. The Eyeball. — The remarkable optical instru- 
ment called the eyeball, or the globe of the eye, upon 
which sight depends, is, as the name indicates, spherical in 
shape. It is not a perfect sphere, since the front part pro- 
jects somewhat beyond the rest, and at the posterior part 
the optic nerve (Fig. 48, n) is united to it, resembling the 
junction of the stem with a fruit. In its long diameter, 
that is, the horizontal or from side to side, it measures a 
little more than an inch ; in other directions it is rather 
less than an inch. In structure, the ball of the eye is firm, 
and its tense round contour may in part be felt by pressing 
the fingers over the closed lids. 

60. The eyeball is composed chiefly of three internal, 
transparent media, called humors; and three investing 
coats, or tunics. The former are the aqueous humor, Fig. 
48, a, the crystalline lens L, and the vitreous humor v. 
Of these the lens alone is solid. The three coats of the 
eyeball are called the sclerotic s, the choroid ch, and the 
retina e. This arrangement exists in respect to five-sixths 
of the globe of the eye, but in the anterior one-sixth, these 
coats are replaced by the cornea c, which is thin and trans- 
parent, so that the rays of light pass freely through it, as 
through a clear window-pane. 

61. In shape, the cornea is circular and prominent, 
resembling a miniature watch-glass, about -}-% of an inch 
thick. In structure, it resembles horn (as the name signi- 
fies), or the nail of the finger, and is destitute of blood- 



59. Describe the shape of the eyeball. Its structure. 

60. Of what is the eyeball composed ? State how. 

61 . The shape of the cornea ? Its structure ? The " white of the eye ?" 



204 THE SPECIAL SENSES. 

vessels. The Sclerotic (from scleras, hard) is composed of 
dense, white fibrous tissue, and gives to the eyeball its 
firmness of figure and its white color ; in front, it consti- 
tutes the part commonly called "the white of the eye." 
It is one of the strongest tissues in the body; it possesses 
very few vessels, and is not very sensitive. It affords pro- 
tection to the extremely delicate interior parts of the eye ; 
and the little muscles which effect its movements are in- 
serted into the sclerotic a short distance behind the cornea 
(see Fig. 48, t, z). It is perforated posteriorly to admit the 
optic nerve. 

62. The Choroid is the second or middle coat of the eye- 
ball, and lies closely attached to the inner surface of the 
sclerotic. Unlike the latter tunic, its structure is soft and 
tender, it is dark in color, and possesses a great abundance 
of blood-vessels. Its dark color is due to a layer of dark 
brown or chocolate-colored cells spread out over its inner 
surface. This dark layer serves to absorb the rays of light 
after they have traversed the transparent structures in 
front of it ; if the rays were reflected from side to side 
within the eye, instead of being thus absorbed, confused 
vision would result from the multitude of images which 
would be impressed upon the optic nerve. 

63. This mechanism has been unconsciously imitated by 
the opticians, who, when they make a microscope or tele- 
scope, take care that the interior of its tube shall be coated 
with a' thick layer of black paint or lamp-black; for with- 
out it, a clear delineation of the object to be viewed is im- 
possible. The albinos, in whom these dark cells of the 
choroid are wanting, have imperfect vision, especially in 
the daytime and in strong lights. The dark cells are also 
wanting in white rabbits, and other animals that have red 
or pink eyes ; their vision appears to be imperfect in the 
presence of a bright light. 

62. The second or middle coat of the eyeball ? Its dark color ? 

63. Similar mechanism in microscopes? The albinos ? White rabbits ? 



THE SPECIAL SENSES. 205 

64. The Iris. — Continuous with the choroid, in the front 
part of the globe of the eye, is a thin, circular curtain, 
which occasions the brown, blue, or gray color of the eye 
in different individuals. On account of the varieties of its 
color, this membrane has received the name Iris, which is 
the Greek word for " rainbow" (see Fig. 48, i). A front 
view of it is shown in Fig. 47. The iris is pierced in its 
centre by a round opening, called the pupil (p), which is 
constantly varying in size. In olden times it was spoken 
of as the " apple of the eye." The hinder surface of the 
iris, except in albinos, has a layer of dark coloring matter 
resembling that of the choroid. The iris is a muscular 
organ, and contains two distinct sets of fibres; one of which 
is circular, while the other radiates outward from the pupil. 
The action of these sets of fibres regulates the size of the 
pupil ; for when the circular set acts, the pupil contracts, 
and when the other set acts, the opening expands. Their 
action is involuntary, and depends on the reflex system of 
nerves, which causes the contraction of the pupil when a 
strong light falls upon the eye, and its expansion when 
the illumination is feeble. 

65. The iris, accordingly, serves a very useful purpose 
in regulating the admission of light to the eye. It, how- 
ever, does not act instantaneously; and hence, when we 
pass quickly from a dark room into the bright sunlight, 
the vision is at first confused by the glare of light, but as 
soon as the pupil contracts, the ability to see becomes per- 
fect. On the other hand, when we enter a dark apart- 
ment, such as a cellar, for a short time we can see nothing 
clearly ; but as soon as the pupil expands and admits more 
light, we are enabled to distinguish the surrounding ob- 
jects. Animals of the cat species, and others which prowl 
around after nightfall, are enabled to see in the dark by 

64. What is the iris ? Its construction ? How is the size of the pupil regu- 
lated ? 

65. The admission of light to the eye ? The action of the iris under different 
circumstances ? The lustre of the eye, how affected in youth and old age ? 



206 THE SPECIAL SENSES. 

having the iris very dilatable. The size of the pupil affects 
the lustre of the eye. When it is large, as it usually is dur- 
iog youth, the eye appears clear and brilliant; while in old 
age the pupil is small and the eye is dull. The brilliancy 
of the eye is in part, at least, dependent upon the reflec- 
tion of light from the front surface of the crystalline lens. 

66. Certain poisonous vegetables have the property of 
causing the pupil to dilate, and have been used in small 
doses to increase the beauty of the eye. One of these 
drugs has been so largely used by the ladies for this pur- 
pose, that it has received the name belladonna, from the 
Italian words meaning " beautiful lady." This hazardous 
practice has resulted more than once in the death of the 
person desiring thus to increase her personal attraction. 
The common English name for belladonna is "deadly 
nightshade." (In the diagram on page 214 the shape and 
relations of the iris are more accurately shown than in the 
figure referred to above.) 

67. The Retina constitutes the third and inner coat of 
the globe of the eye. This, the important part of the eye 
that is sensitive to light, is a kind of nervous membrane, 
formed by the expansion of the ultimate filaments of the 
optic nerve. Its texture is soft, smooth, and very thin; 
it is translucent and of an opaline, or grayish-white 
color. It is sensitive to light alone ; and if any form of 
mechanical irritation be applied to it, the sensations of 
touch and pain are not experienced, but flashes of fire, 
sparks, and other luminous appearances are perceived. 
Thus an electric shock given to the eye-ball occasions a 
flash of light ; and a sudden fall, or a blow upon the eye, 
is often apparently accompanied by the vision of " stars." 

68. These phenomena are due to what is termed the 



66. Means used to increase the beauty of the eye? The injurious conse- 
quences ? 

67. What part does the retina constitute ? How formed ? Its texture ? Color ? 
Sensitiveness ? 

68 . Specific energy of the optic nerve ? Trial in Germany ? 



THE SPECIAL SENSES. 207 

" specific energy" of the optic nerve, which nerve, in com- 
mon with the other nerves of special sense, obeys a general 
law of nature, which requires that, whenever one of these 
nerves is stimulated, it shall respond with the sensation 
peculiar to itself. These flashes of retinal light have no 
power to illuminate external objects, although the opposite 
of this statement has been maintained. On the occasion 
of a remarkable trial in Germany, it was claimed by a per- 
son who had been severely assaulted on a very dark night, 
that the flashes of light caused by repeated blows upon the 
head enabled him to see with sufficient distinctness to 
recognize his assailant. But the evidence of scientific 
men entirely refuted this claim, by pronouncing that the 
eye, under the circumstances named, was incapacitated for 
vision. Too intense light occasions a feeling of pain, but 
it is of a peculiar kind, and is termed " dazzling." 

69. All parts of the retina are not equally sensitive, and 
singularly enough, the point of entry of the nerve of sight, 
in the back part of the eyeball, is entirely insensible to light, 
and is called the "blind spot." The existence of this point 
may be proven by a simple experiment. Hold the accom- 




panying figure, on page 207, directly in front of and paral- 
lel with the eyes. Close the left eye, and fix the sight 
steadily on the left-hand circle ; then, by gradually varying 
the distance of the figure from the eye, at a certain dis- 
tance (about six inches), the right-hand circle will disappear, 

69. Sensitiveness of all parts of the retina? Experiment to prove the exist- 
ence of the " blind spot." 



208 THE SPECIAL SENSES. 

but nearer or further than that, it will be plainly seen. 
The other eye may be also tried, with a similar result : if 
the gaze be directed to the right-hand circle, the left one 
will seem to disappear. The experiment may be repeated 
by using two black buttons on the marble top of a bureau, 
or on some other white surface. The blind spot does not 
practically interfere with vision, since the eye is seldom 
fixed immovably on an object, and the insensitive parts of 
the two eyes can never be directed upon the same object at 
the same time. 

70. Impressions made upon the retina are not at once 
lost, but persist a measurable length of time, and then 
gradually fade away. Thus, a bright light or color, gazed 
at intently, cannot be immediately dismissed from sight by 
closing or turning away the eyes. A stick lighted at one 
end, if whirled around rapidly in the dark, presents the 
appearance of an unbroken luminous ring ; and the spokes 
of a rapidly revolving carriage- wheel seem to be merged 
into a plane surface. If an object move too rapidly to pro- 
duce this sort of lasting impression, it is invisible, as in the 
case of a cannon-ball passing through the air in front of 
us. 

71. If a card, painted with two primary colors— as red and 
yellow — be made to rotate swiftly, the eye perceives neither 
of them distinctly ; but the card appears painted with their 
secondary color — orange. The average duration of retinal 
images is estimated at one-eighth of a second ; and it is 
because they thus endure, that the act of winking, which 
takes place so frequently, but so quickly, is not noticed and 
does not interrupt the vision. The retina is easily fatigued 
or deprived of its sensibility. After looking steadfastly at 
a bright light, or at a white object on a black ground, a 
dark spot, corresponding in shape to the bright object, 



•70. Duration of impressions upon the retina ? How illustrated ? 

71. What further illustration? Winking, why it is not noticed. 

•which the retina is fatigued or deprived of sensibility ? How shown ? 






THE .SPECIAL SENSES. 209 

presents itself in whatever direction we look. This spot 
passes away as the retina resumes its activity. 

72. If a bright color be gazed at intently, and the eyes 
then be turned to a white surface, a spot will appear ; but 
its color will be the complement of that of the object. Fix 
the eye upon a red wafer upon a white ground, and on re- 
moving the wafer a greenish spot of the same shape takes 
its place. This result happens because a certain portion of 
the retina has exhausted its power to perceive the red ray, 
and perceives only its complementary ray, which is green. 
The color thus substituted by the exhausted retina is called 
a physiological or accidental color. In some persons the 
retina is incapable of distinguishing different colors, when 
they are said to be affected with " color-blindness." Thus, 
red and green may appear alike, and then a cherry-tree, 
full of ripe fruit, will seem of the same color in every part. 
Railroad accidents have occurred because the engineer of 
the train, who was color-blind, has mistaken the color of a 



73. The Crystalline Lens.— Across the front of the 
eye, just behind the iris, is situated the Crystalline lens, 
enclosed within its own capsule. It is supported in its 
place partly by a delicate circular ligament, and partly by 
the pressure of adjacent structures. It is colorless and per- 
fectly transparent, and has a firm but elastic texture. In 
shape it is doubly convex, and may be rudely compared to 
a small lemon-drop. The front face of the lens is flatter 
than the other, and is in contact with the iris near its 
pupillary margin, as is represented in the diagram on page 
214. It is only one-fourth of an inch thick. 

74. "When this little body becomes opaque, and no longer 
affords free passage to the rays of light, as often happens 

72. How farther shown? How is the result accounted for? "Color-blind- 
ness?" 

73. The location of the crystalline lens? How supported? Its color and 
texture ? Shape ? Size ? 

74. Cataract? Aqueous humor ? Vitreous humor ? 



210 THE SPECIAL SEXSES. 

with the advance of age, an affection termed " cataract" is 
produced. Between the crystalline lens and the cornea is 
a small space which contains the aqueous humor (see Fig. 
48, a). This humor consists of five or six drops of a clear, 
colorless liquid very much like water, as its name implies. 
That part of the globe of the eye lying behind the lens is 
occupied by the vitreous humor, so called from its fancied 
resemblance to melted glass (Fig. 48, v). This humor is a 
transparent, jelly-like mass, enclosed within an exceed- 
ingly thin membrane. It lies very closely applied to the 
retina, or nervous membrane of the eye, and constitutes 
fully two-thirds of the bulk of the eyeball. 

75. The Uses of the Crystalline Lens.— A con- 
vex lens has the property of converging the rays of light 
which pass through it ; and the point at which it causes 



Fig. 50.— The Retinal Image. 

them to meet is termed its focus. If a lens of this descrip- 
tion, such as a magnifying or burning-glass, be held in 
front of an open window, in such a position as to allow 
its focus to fall upon a piece of paper, it will be found to 
depict upon the paper a miniature image of the scene out- 
side of the window. It will be further noticed that the 
image is inverted, or upside down, and that the paper 



75. What ie a lens and its focus ? The miniature image, how produced? 



THE SPECIAL SENSES. 211 

at the place upon which the image is thrown is much 
brighter than any other part. 

76. Now all the transparent structures of the eye, but 
especially the crystalline lens, operate upon its posterior 
part, or retina, as the convex lens acts upon the paper ; that 
is, they paint upon the retina a bright inverted miniature 
of the objects that appear in front of the eye (Fig. 50). 
That this actually takes place may be proved by experi- 
ment. If the eyeball of a white rabbit, the walls of which 
are transparent, be examined while a lighted candle is held 
before the cornea, an image of the candle-flame may be 
seen upon the retina. 

77. The form and structure of the crystalline lens endow 
it with a remarkable degree of refractive power, and en- 
able it to converge all the rays of light that enter it 
through the pupil, to a focus exactly at the surface of the 
retina. When this lens is removed from the eye, as is 
frequently done for the cure of cataract, it is found that 
the rays of light then have their focus three-eighths of an 
inch behind the retina; that the image is four times larger 
than in the healthy eye, that it is less brilliant, and that 
its outline is very indistinct. From this we learn that one 
of the uses of the crystalline lens is to make the retinal 
image bright and sharply-defined, at the same time that it 
reduces its size. Indeed, the small size of the image is a 
great advantage, as it enables the limited surface of the 
retina to receive, at a glance, impressions from a consider- 
able field of vision. 

78. As the image upon the retina is inverted, how does 
the mind perceive the object in its true, erect position ? 
Many explanations have been advanced, but the simplest 
and most satisfactory appears to be found in the fact that 



76. How are figures painted upon the retina ? How proved ? 

77. What can be eaid in respect to the form and structure of the crystalline 
lens? 

78. How ie the inverted image upon the retina presented in its true position to 
the mind ? 



212 THE SPECIAL SENSES. 

the retina observes no difference, so to speak, between the 
right and left or the upper and lower positions of objects. 
In fact, the mind is never conscious of the formation of a 
retinal image, and until instructed, has no knowledge that 
it exists. Consequently, our knowledge of the relative 
location of external objects must be obtained from some 
other source than the retina. The probable source of this 
knowledge is the habitual comparison of those objects with 
the position of our own bodies: thus, to see an elevated 
object, we know we must raise the head and eyes; and to 
see one at our right hand, we must turn the head and eyes 
to the right. 

79. Long-sight or Hyperopia, and Short-sight 
or Myopia. — The eye is not in all cases perfectly 
formed. For example, persons may from birth have the 
cornea too prominent or too fiat, or the lens may be too 
thick or too thin. In either of these conditions sight will 



Fig. 51.— The Different Shapes of the Globe of the Eye. 

N, The Natural Eye. M, The Short-sighted Eye. 

H, The Long-sighted Eye. S, Parallel Rays^from the Sun. 

be more or less defective from the first, and the defect will 
not tend to disappear as life advances. The most common 
imperfection, however, is in the shape of the globe ; which 
may be short (Fig. 51, h), as compared with the natural 
eye, n, or it may be too long, m. 

80. When the globe is short, objects can only be clearly 

79. The uniform perfection of the eye? Examples? The most common im- 
perfection ? 

80. How is " long-sight" explained ? " Short-sight ?" 



THE SPECIAL SENSES. 213 



seen that are at a distance, and the condition of the vision 
is known as "long-sight," or hyperopia. It will be ob- 
served, by reference to Fig. 51, that the focns of the 
rays of light would fall behind the retina of this eye. 
When the globe is too long, objects can only be clearly seen 
that are very near to the eye; and the condition resulting 
from this defect is termed " short-sight," or myopia. The 
focus of the rays of light is, in this case, formed in the 
interior of the eye in front of the retina. 

81. Long-sight, or hyperopia, is common among young 
persons, even more so than short-sight, and must not be 
confounded with the defect known as the " far sight" of 
old people; although in both affections the sight is im- 
proved by the use of convex glasses. Children not infre- 
quently discover that they see much better when they 
chance to put on the spectacles of old persons. For the 
relief of short-sight, concave glasses should be employed ; 
as they so scatter the rays of light as to bring the focus to 
the retina, and thus cause the vision of remote objects 
to become at once distinct. That form of "squint," in 
which the eyes are turned inward, is generally dependent 
upon long-sight, while that rarer form, when they turn 
outward, is due to short-sight. 

82. The Function of Accommodation. — If, after 
looking through an opera-glass at a very distant object, it 
is desired to view another nearer at hand, it will be found 
impossible to obtain a clear vision of the second object un- 
less the adjustment of the instrument is altered ; which is 
effected by means of the screw. If an object, like the end of 
a pencil, be held near the eye, in a line with another object 
at the other side of the room, or out of the window, and 
the eye be fixed first upon one and then upon the other, it 
will be found that when the pencil is clearly seen, the fur- 

8 1 . Long-eight, how common ? With what must it not be con ounded ? Kind 
of glasses for short-sight ? Why ? Squint ? 

82. What is stated in connection with the opera-glass? Experiment with 
pencil and distant object ? 



214 THE SPECIAL SENSES. 

ther object is indistinct; and when the latter is seen 
clearly, the pencil appears indistinct ; and that it is im- 
possible to see both clearly at the same time. Accordingly, 
the eye must have the capacity of adjusting itself to dis- 
tances, which is in some manner comparable to the action 
of the screw of the opera-glass. 

83. This, which has been called the function of accom- 
modation, is one of the most admirable of all the powers 
of the eye, and is exercised by the crystalline lens. It 
consists essentially in a change in the curvature of the 
front surface of the lens, partly through its own elasticity, 
and partly through the action of the ciliary muscle. 




Fig. 52.— The Function of Accommodation. 



When the eye is at rest, that is, when accommodated for a 
distant object, the lens is natter and its curvature dimin- 
ished (see Fig. 52) ; but when strongly accommodated for 
near vision the lens becomes thicker, its curvature in- 
creases, and the image on the retina is made more sharp 
and distinct. Since a strong light is not required in view- 
ing near objects, the pupil contracts, as is shown in the 
left-hand half of the diagram. 

83. Function of accommodation ? In what does it consist ? How is the func- 
tion explained ? 



THE SPECIAL SENSES. 215 

84. Old-sight, or Presbyopia. — But this marvel- 
lously beautiful mechanism becomes worn with use; or, 
more strictly speaking, the lens, like other structures of the 
body, becomes harder with the approach of old age. The 
material composing the lens becomes less elastic, the power 
to increase its curvature is gradually lost, and as a conse- 
quence, the person is obliged to hold the book further away 
when reading, and to seek a stronger light. In a word, the 
function of accommodation begins to fail, and is about the 
first evidence that marks the decline of life. By looking at 
the last preceding diagram, and remembering that the in- 
creased curvature of the lens cannot take place, it will be 
at once understood why old-sight is benefitted in near 
vision by the convex lens, such as the spectacles of old 
people contain. It acts as a substitute for the deficiency 
of the crystalline lens. 

85. The Sense of Hearing. — Sound. — Hearing, or 
audition, is the special sense by means of which we are 
made acquainted with sound. What is sound ? It is an 
impression made upon the organs of hearing, by the vibra- 
tions of elastic bodies. This impression is commonly prop- 
agated by means of the air, which is thrown into delicate 
undulations, in all directions from the vibrating sub- 
stance. When a stone is thrown into smooth water, a wave 
of circular form is set in motion, from the point where the 
stone struck, which constantly increases in size and dimin- 
ishes in force, as it advances. 

86. Somewhat resembling this, is the undulation, or 
sound-wave, which is imparted by a sonorous vibration to 
the surrounding atmosphere. Its shape, however, is spher- 
ical, rather than circular, since it radiates upward, down- 
ward, and obliquely as well as horizontally, like the wave 

84. Change of sight with the approach of old age ? Explain the change ? 

85. Hearing or audition? What is sound? How propagated commonly? 
Stone thrown in water ? 

86. Sound-wave in the atmosphere ? Its shape ? Rate of motion ? Sound, in 
water, air, and solid bodies ? 



216 THE SPECIAL SENSES. 

in water. The rate of motion of this spherical wave of 
air is about 1050 feet per second, or one mile in five 
seconds. In water, sound travels four times as fast as in 
air, and still more rapidly through solid bodies ; along an 
iron rod, its velocity is equal to two miles per second. 

87. The earth, likewise, is a good conductor of sound. 
It is said that the Indian of our western prairies can, by 
listening at the surface of the ground, hear the advance of 
a troop of cavalry, while they are still out of sight, and 
can even discriminate between their tread and that of a 
herd of buffaloes. Solid substances also convey sounds 
with greater power than air. If the ear be pressed against 
one end of a long beam, the scratching of a pin at the 
other extremity may be distinctly heard, which will not be 
at all audible when the ear is removed from the beam. 
Although air is not the best medium for conveying sound, 
it is necessary for its production. Sound cannot be pro- 
duced in a vacuum, as is shown by ringing a bell in the 
exhausted receiver of an air-pump, for it is then entirely 
inaudible. But let the air be readmitted gradually, then 
the tones become more and more distinct, and when the 
receiver is again full of air, they will be as clear as usual. 

88. All sonorous bodies do not vibrate with the same 
degree of rapidity, and upon this fact depends the pitch of 
the sounds that they respectively produce. The more fre- 
quent the number of vibrations within a given time, the 
higher will be the pitch ; and the fewer their number, the 
lower or graver will it be. Now, the rate of the successive 
vibrations of different notes has been measured, and it has 
thus been found that if they are less than sixteen in a 
second, no sound is audible; while if they exceed 60,000 
per second the sound is very faint, and is painful to the 



87. The earth as a conductor of sound ? To what has the western Indian been 
taught ? Solid substances as conductors ? As regards sound, in what respect is 
air necessary ? Sound in a vacuum ? 



THE SPECIAL SENSES. 217 

ear. The extreme limit of the capacity of the human ear 
maybe considered as included between these points; but 
the sounds which we ordinarily hear are embraced be- 
tween 100 and 3,000 vibrations per second. 

89. The ear, which is the proper organ of hearing, is the 
most complicated of all the structures that are employed 
in the reception of external impressions. The parts of 
which it is composed are numerous, and some of them are 
extremely small and delicate. Nearly all these parts are 
located in an irregularly shaped cavity hollowed out in the 
temporal, or " temple," bone of each side of the h^ad. 
That part of the bone in which the auditory cavity is 
placed has the densest structure of all bones of +.he body, 
and has therefore been called the "petrous," or rocky part 
of the temporal bone. In studying the ear, i t is necessary 
to consider it as divided into three portions, which are 
called, from their relative positions, the external ear, the 
middle ear, and the internal ear. (In the diagram, Fig. 53, 
A, the first is not shaded, the seconc 1 is lightly shaded, and 
the last has a dark background. ) 

90. The External Ear. — The external portion of the 
organ of hearing, designated in Fig. 53, A, includes, first, 
that outer part (a), which is commonly spoken of as "the 
ear," but which in fact is only the portal of that organ ; 
and, secondly, the audito* y canal (b). The former consists 
of a flat flexible piece of cartilage, projecting slightly from 
the side of the head, a otached to it by ligaments, and sup- 
plied with a few weak muscles. Its surface is uneven, and 
curiously curved, ar.d from its resemblance to a shell, it 
has been called the concha. It probably serves to collect 
sounds, and to gbre them an inward direction ; although 
its removal is said not to impair the acuteness of hearing 
more than a few days. 

90. Of what does the external portion of the organ of hearing consist? De- 
scribe the portal of that organ known as the ear. Its use ? 



218 



THE SPECIAL SENSES. 



91. In those animals whose hearing is more delicate 
than that of man, the corresponding organ is of greater 
importance, it being larger and supplied with muscles of 
greater power, so that it serves as a natural kind of ear- 
trumpet, which is easily movable in the direction of any 
sound that attracts the attention of the animal. Bold, 
predaceous animals generally have the concavity of this 




Fig. 53.— The Ear and its Different Parts. 

A, Diagram of the Ear. 

o, ft, External Ear. d. Middle Ear. 

c, Membrane tympani. e, Internal Ear. 

B to B"\ Bones of the fiddle Ear (magnified). 

C, The Labyrinths, or Internal Ear (highly magnified). 

organ directed forward, while in timorous animals, like the 
rabbit, it is directed backward. Fishes have no outer ear, 
but sounds are transmitted directly through the solid bones 
of the head, to the internal organ of hearing. 

92. The auditory canal (Fig. 53, '-A, b), which is con- 
tinuous with the outer opening of tht- ear, is a blind pas- 
sage, an inch and a quarter in length, l its inner extremity 
being bounded by a closely-fitting, circular membrane. 
This canal is of oval form, is directed forward and inward, 



91 . The ear in the animals of delicate hearing? 

92. What is the auditory canal ? Describe it. 



Rabbit ? Fishes f 



THE SPECIAL SENSES. 219 

and is slightly curved; so that the inner end is ordinarily 
concealed from view. The pouch of the skin which lines 
this passage is smooth and thin, especially at the lower 
end, where it covers the membrane just mentioned. 

93. As in the case of the nostrils, a number of small, 
stiff hairs garnish the margin of the auditory canal, and 
guard it, to some extent, against the entrance of insects 
and other foreign objects. The skin, too, covering its outer 
half, is furnished with a belt of little glands which secrete 
a yellow, viscid, and bitter substance, called " ear-wax," 
which is especially obnoxious to small insects. As the 
outer layer of this wax-like material loses its useful pro- 
perties, it becomes dry, and falls out of the ear in the form 
of minute, thin scales, a fresh supply being furnished from 
the little glands beneath. In its form, the auditory canal 
resembles the tube of an ear-trumpet, and serves to convey 
the waves of sound to the middle portion of the ear. 

94. The Middle Ear, or Tympanum.— The middle 
ear is a small cavity, or chamber, of irregular shape, about 
one-fourth of an inch across from side to side, and half an 
inch long (see Fig. 53, A, d). From the peculiar arrange- 
ment of its various parts it has very properly been called 
the tympanum, or the "drum of the ear." The middle 
ear, like the external canal, contains air. 

95. The circular membrane, already mentioned as clos- 
ing the auditory canal, is the partition which separates 
the middle from the external ear, and is called the mem- 
hrana tympani (c), and may be considered as the outer head 
of the drum of the ear. It is sometimes itself spoken of as 
the " drum," but this is incorrect ; since a drum is not a 
membrane, but is the hollow space across which the mem- 
brane is stretched. This membranous drum-head is very 
tense and elastic, and so thin as to be almost transparent ; 



93. How is it guarded and protected ? Ear-wax ? 

94. What is the middle ear ? Why called tympanum? 

95. What is the membrana tympani ? Describe it. 



220 THE SPECIAL SENSES. 

its margin is fastened into a circular groove in the adjacent 
bone. Each wave of sound that impinges against this 
delicate membrane causes it to vibrate, and it, in turn, 
excites movements in the parts beyond. 

96. Within the tympanum is arranged a chain of re- 
markable " little bones," or ossicles. They are chiefly three 
in number, and from their peculiar shapes bear the follow- 
ing names: malleus, or the mallet; incus, or the anvil; 
and stapes, or the stirrup. A fourth, the smallest bone in 
the body, in early life intervenes between the incus and 
stapes, but at a later period it becomes a part of the incus. 
It is called the orbicular bone. Small as are these ossicles — 
and they, together, weigh only a few grains — they have 
their little muscles, cartilages, and blood-vessels, as per- 
fectly arranged as the larger bones of the body. One end 
of the chain of ossicles, the mallet, is attached to the mem- 
brane of the tympanum, or outer drum-head, while the 
other end, the stirrup, is firmly joined by its foot-piece to 
a membrane in the opposite side of the cavity. The chain, 
accordingly, hangs suspended across the drum between the 
two membranes ; and when the outer one vibrates under 
the influence of the sound-wave, the chain swings inward 
and transmits the vibration to the entrance of the inner 
ear. 

97. The musical instrument, the drum, is not complete 
if the air within be perfectly confined : we therefore find in 
all instruments of this kind a small opening in the side, 
through which air may pass freely. By this means the 
pressure of the air upon the vellum which forms the head 
of the drum is made equal upon all sides, and the resonance 
of the drum remains unaffected by the varying density of 
the atmosphere. It will, therefore, emit its proper sound, 
whether it be struck in the rarified air of the mountain- 
top, or in the condensed air of a mine. The tympanum, 



THE SPECIAL SENSES. 



221 



or drum of the ear, in like manner has an opening by 
means of which it communicates freely with the external 
air. This opening is a narrow canal, about an inch and a 
half long, called the Eustachian tube, after the name of its 
discoverer, Eustachius. 

98. The course of this passage is indicated in Fig. 54, i, 
directed downward and inward : its other extremity opens 
into the upper part of the throat. The passage itself is 




"Fig. 54.— Section op the Right Ear. 

A, The Concha. E, Incus, or Anvil. 

B, Auditory Canal. M, Malleus, or Mallet. 

C, Membrane of the Dram, I, Eustachian Tube. 

(the lower half.) G, Semicircular Canals. 

D, A small muscle. H, Cochlea, or snail's shell. 

ordinarily closed, but whenever the act of swallowing or 
gaping takes place, the orifice in the throat is stretched 
open, and the air of the cavity of the tympanum may then 
be renewed. Air may at will be made to enter through 
this tube, by closing the mouth and nose, and then trying 



98. What can you state of the action of the Eustachian tube ? 



222 THE SPECIAL SENSES. 

to force air through the latter. When this is done, a dis- 
tinct crackle or clicking sound is perceived, due to the 
movement of the membranes, and of the little bones of the 
ear. 

99. The Eustachian tube serves, also, as an escape-pipe 
for the fluids which form within the middle ear; and 
hence, when its lining membrane becomes thickened, in 
consequence of a cold, or sore throat, and the passage is 
thus more or less choked up, the fluids are unable to escape 
as usual, and therefore accumulate within the ear. When 
this takes place, the vibrations of the membrane are inter- 
fered with; the sounds heard appear muffled and indis- 
tinct; and a temporary difficulty of hearing, which is 
known as "throat-deafness," is the result. This result re- 
sembles the effect produced by interrupting the vibrations 
of a sonorous body, such as all are familiar with ; if the 
finger be placed upon a piano-string or bell when it is 
struck, the proper sound is no longer fully and clearly 
emitted. But the primary use of this tube is to afford a 
free communication between the middle ear and the exter- 
nal atmosphere, and thus secure an equal pressure upon 
both sides of the membrane of the drum of the ear, however 
the density of the atmosphere may vary. If, from undue 
tension of the membranes, pain is experienced in the ears, 
when ascending into a rare atmosphere, as in a balloon, or 
descending into a dense one, as in a diving-bell, it may be 
relieved by repeating the act of swallowing, from time to 
time, in order that the inner and outer pressure may thus 
be promptly equalized. 

100. The Internal Ear, or Labyrinth. — The most 
essential part of the organ of hearing is the distribution of 
the auditory nerve. This is found within the cavity of the 
internal ear, which, from its exceedingly tortuous shape, 



99. What other purpose does the Eustachian tube serve ? How is this shown? 
' Throat-deafness V Primary use of the Eustachian tube ? 

1 00. The essentia] part of the organ of hearing ? Its location ? Formation ? 



THE SPECIAL SENSES. 223 

has been termed the labyrinth (see Fig. 53, c). This 
cavity is hollowed out in dense bone, and consists of three 
parts ; the vestibule (a), or ante-chamber, which is connected 
with the other two ; the cochlea (b), or snail's shell ; and the 
three semicircular canals (c). The manner in which the 
nerve of hearing is distributed is remarkable, and is pecu- 
liar to this nerve. In the vestibule and the canals its 
fibres are spread put over the inner surface, not of the bony 
cavity but of a membranous bag, which conforms to and 
partially fills that cavity ; and: which floats in it, being 
both filled and surrounded with a clear, limpid fluid. 

101. A singular addition to the mechanism of hearing is 
observed within this membranous bag of the labyrinth 
This consists of two small oval ear-stones, and a quantity ' 
of fine powder of a calcareous nature, which is called " ear- 
sand." When examined under the microscope, these sandy 
particles are seen to lie scattered upon and among the 
delicate filaments of the auditory nerve; and it is probable, 
that as the tremulous sound-wave traverses the fluid of the 
vestibule, the sand rises and falls upon the nerve filaments, 
and thus intensifies the sonorous impression. 

102. In the cochlea, or snail's shell, which contains the 
fluid, but no membrane, the nerve ramifies upon a spiral 
shelf, which, like the cochlea itself, takes two and a half 
turns, growing continuously smaller as it winds upward. 
As many as three thousand nerve fibres of different lengths 
have been counted therein ; which, it has been thought, 
form the grand, yet minutely small key-board, upon which 
strike all the musical tones that are destined to be con- 
veyed to the brain. The vestibule, it is also supposed, takes 
cognizance of noise as distinguished from musical sounds ; 
while the office of the semicircular canals is, in part at 
least, to prevent internal echoes, or reverberations. 



101 . Where is the " ear-sand 1 ' found ? Give the theory as to its use. 

102. In the cochlea or snail's shell? " Key-board" in the internal ear ? The 

vestibules ? Semicircular canals ? 



224 THE SPECIAL SENSES. 

103. The vestibule communicates with the chain of 
bones of the middle ear by means of a small opening, 
called the " oyal window/' or fenestra ovalis. Across this 
window is stretched the membrane, which has already 
been alluded to as being joined to the stirrup-bone of the 
middle ear. Through this window, then, the sound-wave, 
which traverses the external and middle ear, arrives at last 
at the labyrinth. The limpid fluid which the latter con- 
tains, and which bathes the terminal fibres of the nerve of 
hearing, is thus agitated, the nerve-fibres are excited, and 
a sonorous impression is conducted to the brain, or, as we 
say, a sound is heard. 

104. Protection of the Sense of Hearing. — From 
what has been seen of the complicated parts which com- 
pose the organ of hearing, it is 'evident that while many 
of them possess an exquisite delicacy of structure, Nature 
has well and amply provided for their protection. We 
have observed the concealed situation of the most impor- 
tant parts of the mechanism of the ear, the length of its 
cavity, its partitions, the hardness of its walls, and its 
communication with the atmosphere ; all these provisions 
rendering unnecessary any supervision or care on our part 
in reference to the interior of the ear. But in respect to 
its external parts, which are under our control and within 
the reach of harm, it is otherwise. We may both observe 
the dangers which threaten them, and learn the means 
necessary to protect them. 

105. One source of danger to the hearing consists in 
lowering the temperature of the ear, especially by the 
introduction of cold water into the auditory canal. Every 
one is familiar with the unpleasant sensation of distension 
and the confusion of sounds which accompany the filling 
of the ear with water when bathing : the weight of the 

103. With what does the vestibule communicate? What is the theory by 
which sound is conducted to the brain ? 

1 04. The formation of the organ of hearing with a view to its protection ? 

105. Danger to which the hearing may be subjected ? Advice ? 



THE SPECIAL SENSES. 225 

water within it really distends the membrane, and the cold 
chills the adjacent sensitive parts. It is not surprising, 
therefore, that the frequent introduction of cold water and 
its continued presence in the ear enfeeble the sense of 
hearing. Care should be taken to remove water from the 
ear after bathing, by holding the head on one side, and, 
at the same time, slightly expanding the outer orifice, so 
that the fluid may run out. For a like reason, the hair 
about the ears should not be allowed to remain wet, but 
should be thoroughly dried as soon as possible. 

106. It may be stated as a general rule, to which there 
are but few exceptions, that no cold liquid should ever be 
allowed to enter the ear. When a wash or injection is 
rendered necessary, it should always be warmed before use. 
The introduction of cold air is likewise hurtful, especially 
when it pours through a crevice directly into the ear, as it 
may often do through the broken or partially closed win- 
dow of a car. The avoidance of this evil gives rise to 
another almost as great ; namely, the introduction of cot- 
ton or other soft substances into the ear to prevent it from 
" catching cold." This kind of protection tends to make 
the part unnaturally susceptible to changes of tempera- 
ture, and its security seems to demand the continued pres- 
ence of the " warm" covering. As a consequence of its 
presence, sounds are not naturally conveyed, and the sen- 
sitiveness of the nerve of hearing is gradually impaired. 

107. The chief source of injury, however, to the ear is 
from the introduction of solid substances into the auditory 
canal, with the design of removing insects or other foreign 
objects that have found their way into the ear ; or with 
the design of scraping out the ear-wax. For displacing a 
foreign object, it is usually sufficient to syringe the ear 
gently with warm water, the head being so held that the 



1 06. The general rule as to the use of water for the ear ? 

107. Chief source of injury to the ear? Directions for removing foreign ob- 
jects from the ear ? Of a live insect ? 

10* 



226 



THE SPECIAL SENSES. 



fluid easily escapes. If a live insect has gained entrance 
to the ear, it may first be suffocated by pouring a little oil 
upon it, and afterward removed by syringing the ear as 
just mentioned. 

108. The removal of ear-wax is generally unnecessary ; 
for, as we have before seen, Nature provides that the excess 
of it shall become dry, and then spontaneously fall out in 
the form of fine scales. The danger from the introduction 
of solid implements into the outer ear is chiefly found in 
the fact that the membrane which lies at the bottom of it 
is very fragile, and that any injury of it is liable to be per- 
manent, and to permanently impair the hearing of the 
injured ear. 



QUESTIONS FOR TOPICAL REVIEW. 

Give as full statements as you can on the following subjects : 



. Production of sensation 177, 

, Variety of sensations 178, 

, General sensibility 179, 

, The sensation of pain 

. The uses of pain 180. 181. 

. Special sensation 182. 

. Organs of touch 183. 

. The sense of touch 181, 185. 

. The delicacy of toach 186. 

. Sensations of temperature and 

weight 187, 

. The organ of taste 188, 

. The sense of taste 189, 

. Relations of taste, etc 190, 

. Influence of education, etc.. 191, 

. The sense of smell 192, 

. The nerve of smell 193, 

. Usee of the sense of smell. .194. 
. The sense of sight 1%, 



ITS 



19. Light, and the optic nerve. .197, 198 

20. The organ of sight 19S, 199 

21. The orbits 199 

22. The eyelids 200, 201 

23. The lachrvmal fluid . . .201. 202, 203 

24. The eyeball 213, 204 

25. The iris 205. 206 

26. The retina 2C6. 207, 208, 209 

27. The crystalline lens 209. 210 

28. Uses of the lens 210,211, 212 

29. Long and short sight 212, 213 

30. Function of accommodation.213, 214 

31. Old sight, or presbyopia 215 

32. Hearing and sound'. . . . .215, 216. 217 

33. The external ear 217, 218, 219 

34. The middle ear 219—222 

35. The internal ear 222. 223, 224 

36. Protection of the sense of hear- 

ing 224, 225, 226 



THE VOICE. 227 



CHAPTER XI. 

The Voice. 

Voice and Speech — The Larynx, or the Organ of the Voice — The Vocal 
Cords — The Laryngoscope — The Production of the Voice — The Use 
of the Tongue — The different Varieties of Voice — The Change of 
Voice — Its Compass — Purity of Tone — Ventriloquy. 

1. Voice and Speech. — In common with the majority 
of the nobler animals, man possesses the power of uttering 
sounds, which are employed as a means of communication 
and expression. In man, these sounds constitute the 
voice ; in the animals, they are designated as the cry. The 
song of the bird is a modification of its cry, which is ren- 
dered possible from the fact that its respiratory function is 
remarkably active. The sounds of the animals are gener- 
ally, but not always, produced by means of their breathing 
organs. Among the insects, they are sometimes produced 
by the extremely rapid vibrations of the wings in the act 
of flight, as in the case of the musquito ; or they are pro- 
duced by the rubbing together of hard portions of the 
external covering of the body, as in the cricket. Almost 
all kinds of marine animals are voiceless. The tambour- 
fish and a few others have, however, the power of making 
a sort of noise in the water. 

2. But man alone possesses the faculty of speech, or the 
power to use articulate sounds in the expression of ideas, 
and in the communication of mind with mind. Speech is 
thus an evidence of the superior endowment of man, and 
involves the culture of the intellect. An idiot, while he 



1 . The uttering of sounds by animals ? How produced ? 

2. The evidence of man's superior endowment? What is stated of the idiot? 
Parrot ? Raven ? 



228 THE VOICE. 



may haye complete vocal organs and full power of uttering 
sounds or cries, is entirely incapable of speech ; and, as a rule, 
the excellence of the language of any people will be found 
to be proportional to their development of brain. Man, 
however, is not the only being that has the power to form 
articulate sounds, for the parrot and the raven may also 
be taught to speak by rote ; but man alone attaches mean- 
ing to the words and phrases he employs. 

3. Speech is intimately related to the sense of hearing. 
A child born deaf is, of necessity, dumb also; not because 
the organs of speech are imperfect, for he can utter cries 
and may be taught to speak, and even to converse in a 
rude and harsh kind of language; but because he can 
form no accurate notion of sound. And a person, whose 
hearing is not delicate, or as it is commonly expressed, 
who "has no ear for music," cannot sing correctly. A per- 
son who has impaired hearing commonly talks in an un- 
naturally loud and monotonous voice. These examples 
show the necessary relation of intelligence and the sense 
of hearing with that form of articulate voice, which is 
termed speech. 

4. The Organ of the Voice. — The essential organ 
of the voice is the Larynx. This has been previously 
alluded to in its relation to the function of respiration ; 
and, in the chapter on that subject, are figured the front 
view of that organ (Fig. 35), and its connection with the 
trachea, tongue, and other neighboring parts (Fig. 38). It 
is situated at the upper part of the neck, at the top of the 
trachea, or tube by which air passes into and out of the 
lungs. The framework of the larynx is composed of four 
cartilages, which render it at once very strong and suffi- 
ciently flexible to enable it to move according to the re- 
quirements of the voice. 

3. Speech and hearing? A deaf child? Person having "no ear for music?" 
Impaired hearing ? What do the examples show ? 

4. Organ of the voice ? Where situated ? Of what is its framework composed ? 



THE VOICE. 



229 



5. The names of the cartilages are (l).the thyroid, 
which is a broad thin plate, bent in the middle and placed 
in the central line of the front part of the neck, where it 
is known as the pomum Adami, or 
Adam's apple (Fig. 55, b), and 
where it may be felt moving up 
and down with each act of swal- 
lowing; (2) the cricoid, which is 
shaped like a seal ring, with the 
broad part placed posteriorly (Fig. 
55, e). At the top of the cricoid 
cartilage are situated the two small 
arytenoid cartilages, the right one 
of which is shown in Fig. 55, c. 
These latter little organs are much 
more movable than the other two, 
and are very important in the pro- 
duction of the voice. They have 
a true ball and socket joint, and 
several small muscles which con- 
tract and relax with as perfect regu- 
larity and accuracy as any of the 
larger muscles of the body. PlG 55 

6. The interior of the larynx is Section ° F T ™J H ^ RYNX AND 
lined with a very sensitive mucous 
membrane, which is much more 
closely adherent to the parts be- 
neath than is usually the case with 
membranes of this description. The epiglottis (a), con- 
sisting of a single leaf-shaped piece of cartilage, is attached 
to the front part of the larynx. It is elastic, easily moved, 
and fits accurately over the entrance to the air-passages 
below it. Its office is to guard these delicate passages and 
the lungs against the intrusion of food and other foreign 




, The Epiglottis. 
B, The Thyroid Cartilage. 
", Arytenoid Cartilage. 
Ventricle of the Larynx. 

E, Cricoid Cartilage. 

F, Right Vocal Cord. 
H, The Trachea. 



5. Names, formation, and situation of the cartilages ? 

6, Lining of the interior of the larynx ? The epiglottis ? 



230 THE VOICE. 

articles, when the act of swallowing takes place. It also 
assists in modifying the voice. 

7. The Vocal Cords. — Within the larynx, and stretched 
across it from the thyroid cartilage in front to the aryte- 
noid cartilages behind, are placed the two sets of folds, 
called the vocal cords. The upper of these, one on each 
side, are the false cords, which are comparatively fixed and 
inflexible. These are not at all essential to the formation 
of vocal sounds, for they have been injured, in those lower 
animals whose larynx resembles that of man, without ma- 
terially affecting their characteristic cries. Below these, 
one on each side, are the true vocal cords (Fig. 55, f), 
which pursue a similar direction to the false cords, namely, 
from before backward. But they are composed of a highly 
elastic, though strong tissue, and are covered with a thin, 
tightly-fitting layer of mucous membrane. Their edges 
are smooth and sharply defined, and when they meet, as 
they do in the formation of sounds, they exactly match 
each other. 

8. Between the true and false vocal cords is a depression 
on each side, which is termed the ventricle of the larynx 
(Fig. 55, d). The integrity of these true cords, and their 
free vibration, are essential to the formation of the tones 
and the modulation of the natural voice. This is shown 
by the fact that, if one or both of these cords are injured 
or become diseased, voice and speech are compromised; 
or when the mucous membrane covering them becomes 
thickened, in consequence of a cold, the vocal sounds are 
rendered husky and indistinct. When an opening is made 
in the throat below the cords, as not infrequently happens 
in consequence of an attempt to commit suicide, voice is 
impossible except when the opening is closed by external 
pressure. 

7. Where are the vocal cords ? The false cords ? The true cords? 

8. Where i? the ventricle of the larynx? The essentials to the formation of the 
tones and modulation of the voice ? 



THE VOICE. 



231 



9. The interval or space between the true cords of the 
voice is constantly varying, not only when their vocal 
function is in exercise, but also during the act of respira- 
tion. Every time the lungs are inflated, the space 
increases to make wide the entrance for the air ; and dimin- 
ishes slightly during expiration. So that these little cords 
move gently to and fro in rhythm with the expansion and 
contraction of the chest in breathing. These movements 
and others may be seen to take place, if a small mirror 
attached to a long handle be placed back into the upper 
part of the throat; the handle near the mirror must be 




Pig. 56. 
A View op the Vocal Cords by Means of the Laryngoscope. 

bent at an angle of 45°, so that we may look "around the 
corner/' so to speak, behind the tongue. The position 
which the mirror must assume will be understood by 
reference to Fig. 38. A view of what may be seen under 
favorable circumstances, during tranquil inspiration is 
represented in Fig. 56. The vocal cords are there shown as 
narrow, white bands, on each side of the central opening, 
and since the image is inverted, the epiglottis appears up- 
permost. The rings partly seen through the opening be- 
long to the trachea. This little mirror is the essential part 

9. Variation in the interval between the true cords of the voice? Experiment 
with the mirror ? 



232 THE VOICE. 



of an instrument, which is called the laryngoscope, and, 
simple as it may seem, it is accounted one of the most val- 
uable of the recently invented appliances of the medical 
art. 

10. The Production of the Voice. — During ordi- 
nary tranquil breathing no sound is produced in the lar- 
ynx, true vocal tones being formed only during forcible 
expiration, when, by an effort of the will, the cords are 
brought close together, and are stretched so as to be very 
tense. The space between them is then reduced to a 
narrow slit, at times not more than y^ of an inch in 
width ; and the column of expired air being forced through 
it causes the cords to vibrate rapidly, like the strings of a 
musical instrument. Thus the voice is produced in its 
many varieties of tone and pitch; its intensity, or loud- 
ness, depending chiefly upon the power exerted in expell- 
ing the air from the lungs. When the note is high, the 
space is diminished both in length and width ; but when it 
is low, the space is wider and longer (Fig. 57, B, c), and 
the number of vibrations is fewer within the same period 
of time. 




Fig. 57. 

The Different Positions of the Vocal, Cords. 

A, The position during inspiration. B, In the formation of low notes. 

C, In the formation of high notes. 

11. The personal quality of the voice, or that which en- 
ables us to recognize a person by his speech, is mainly due 
to the peculiar shape of the throat, nose, and mouth, and 

10. The formation of true vocal tones ? 

1 1 . To what is the personal quality of the voice mainly due ? What aids are 
there ? 



THE VOICE. 233 

the resonance of the air contained within those cavities. 
The walls of the chest and the trachea take part in the 
resonance of the voice, the air within them vibrating at 
t§J ;^ame time with the parts above them. This may be 
tested by touching the throat or breast-bone, when a 
strong vocal effort is made. The teeth and the lips also 
are important, as is shown by the unnatural tones emitted 
by a person who has lost the former, or by one who is 
affected with the deformity known as "hare-lip." The 
tongue is useful, but not indispensable to speech ; the case 
of a woman is reported, from whom nearly the whole 
tongue had been torn out, but who could, nevertheless, 
speak distinctly and e^en sing. 

12. The varieties of voice are said to be four in num- 
ber ; two, the bass and tenor, belonging to the male sex ; 
and two, the contralto or alto, and soprano, peculiar to the 
female. The baritone voice is the name given to a variety 
intervening between the bass and tenor. In man, the 
voice is strong and grave; in woman, soft and high. In 
infancy and early youth, the voice is the same in both 
sexes, being of the soprano variety : that of boys is both 
clear and loud, and being susceptible of considerable train- 
ing, is highly prized in the choral services of the church 
and cathedral. At about fourteen years of age the voice is 
said to change ; that is, it becomes hoarse and unsteady by 
reason of the rapid growth of the larynx. In the case of 
the girl, the change is not very marked, except that the 
voice becomes stronger and has a wider compass ; but in 
the boy, the larynx nearly doubles its size in a single year, 
the vocal cords grow thicker, longer, and coarser, and the 
voice becomes masculine in character. During the prog- 
ress of this change, the use of the voice in singing is inju- 
dicious. 

13. The ordinary range of each of the four varieties of 

12. Varieties of voice? The baritone? The voice in early youth ? 

1 3 j The range of the voice ? Result of careful training of the vocal organs ? 



234 THE VOICE. 

the voice is about two octayes ; but this is exceeded in the 
case of several celebrated vocalists. Madame Parepa-Rosa 
has a compass of three full octaves. When the vocal or- 
gans have been subjected to careful training, and are 
brought under complete control of the will, the tension 
of the cords become exact, and their vibrations become 
exceedingly precise and true. Under these circumstances 
the voice is said to possess "purity" of tone, and can be 
heard at a great distance, and above a multitude of other 
sounds. The power of a pure voice to make itself heard 
was recently exemplified in a striking manner : at a musi- 
cal festival held in an audience-room of extraordinary size, 
and amid an orchestra of a thousand instruments and a 
chorus of twelve thousand voices, the artist named above 
also sang ; yet such was the purity and strength of her 
voice that its notes could be clearly heard rising above the 
vast waves of sound produced by the full accompaniment 
of chorus and orchestra. 

14. In the production of the articulate sounds of speech, 
the larynx is not directly concerned, but those sounds 
really depend upon alterations in the shape of the air- 
passages above that organ. That speech is not necessarily 
due to the action of the larynx is proven by the following 
simple experiment. Let an elastic tube be passed through 
the nostril to the back of the mouth. Then, while the 
breath is held, cause the tongue, teeth, and lips to go 
through the form of pronouncing words, and at the same 
time, let a second person blow through the tube into the 
mouth. Speech, pure and simple, or, in other words, a 
whisper is produced. Still further continue the experi- 
ment, while permitting vocal sounds to be made, and there 
will be produced a loud and whispering speech at the same 
moment ; thus showing that voice and speech are the re- 
sult of two distinct acts. Sighing, in like manner, is pro- 

1 4. The production of the articulate sounds ? What experiment is mentioned ? 



THE VOICE. 235 

duced in the mouth and throat ; if, however, a vocal sound 
be added, the sigh is changed into a groan. 

15. Ventriloquism is a peculiar modification of natu- 
ral speech, which consists in so managing the voice that 
words and sounds appear to issue, not from the person, 
but from some distant place, as from the chimney, cellar, 
or the interior of a chest. The original meaning of the 
word ventriloquism (that is, speaking from the belly), in- 
dicates the early belief that this mode of speech was de- 
pendent upon the possession and use of some special organ 
besides the larynx and mouth ; but at the present time, it 
is known that it is produced by these organs alone, and 
that the sources of deception consist on the part of the 
performer, in the dexterous management of the voice, to- 
gether with a talent for mimicry ; and, on the part of the 
auditory, in the liability of the sense of hearing to error in 
respect to the direction of sounds. The ventriloquist not 
only seems to " throw his voice/' as it is said, or simulates 
the sound as it usually appears at a distance with but lit- 
tle motion of the lips and face, but he imitates the voices 
of an infant and of a feeble old man, of a drunken man 
disputing with an exasperated wife, the broken language of 
a foreigner, the cry of an animal in distress, demonstrating 
that the performer must be proficient in the art of mimicry. 
Ventriloquism was known to the ancient Komans and 
Greeks; and it is thought that the mysterious responses 
that were said to issue from the sacred trees and shrines 
of the oracles at Dodona and Delphi, were really uttered 
by priests who had the power of producing this form of 
speech. 

15. What is ventriloquism ? Indication of the original meaning of the word ? 
How are the ventriloquous sounds produced ? 



236 THE MICROSCOPE. 



chapter xii. 

The Use of the Microscope ik the Study of 
Physiology. 

1. The Law of the Tissues. — The will of an infinite 
Creator is obeyed by atoms as well as by worlds. He has 
seen fit to commit all the functions of life to structures or 
tissues so small as to be invisible to the naked eye. A 
muscle, for example, as we have already learned, is com- 
posed of innumerable filaments, visible only by the aid of 
the microscope; and the power of the muscular mass is 
but the sum of the contractile power of the filaments 
which enter into its composition. Again, each cell of the 
liver, invisible to unassisted sight, is a secreting organ, and 
the liver performs as much duty as the sum of these mi- 
nute organs renders possible and no more. 

2. The Necessity of the Microscope. — If, there- 
fore, we would know the real structure of the human 
body, we must make use of the microscope. We are not at 
liberty either to use it or not ; we must have recourse to it 
in order to obtain a real knowledge of the human body. 
Our eyes are constructed for the common offices of life, to 
provide for our wants and guard us from the ordinary 
sources of danger ; but by arming them with lenses, the 
real structure of plants and animals is revealed to our 
intelligence ; and enemies, otherwise invisible, that lie in 
wait in the air we breathe, and in our daily food and drink, 
to destroy life, are guarded against, 

3. Convex lenses, or magnifying glasses, are disks 
of glass or other transparent substance, which have the 



1 . The will of the Creator, hy what obeyed ? The power of a muscle ? 
Amount of duty performed by the liver ? 

2. Necessity for using the microscope ? The advantages gained hy its use ? 

3. What are convex lenses? Kind of lenses used in microscopes? Experi- 
ment ? Picture thrown upon the eye ? Derivation of the word microscope ? 



THE MICROSCOPE. 237 



property of picturing upon the retina of the eye an 
image of an object larger than the image produced there 
without their aid. The glasses used in microscopes are 
either double convex lenses (a) or plano-convex lenses (b). 
a b 

I ) 

If a double convex lens or a plano-convex one be placed 
over a hole in the shutter of a darkened room, or over 
the key-hole of a door, and a piece of paper be held at a 
proper distance, a picture of all objects in front of the 
lens will be thrown on the paper, as in the camera-obscura 
or the magic-lantern. Now, in the same manner, a lens 
throws a picture of objects to which it is directed on the 
retina of the eye, and when that picture is larger than the 
image made in the eye by the object, without the aid of 
the lens, it is magnified, or the lens has served as a micro- 
scope, so called, from its use in seeing small objects, from 
mikros, small, and skopeo, to see. 

4. Different Kinds of Microscopes. — Microscopes 
are either simple or compound. The glasses of magnifying 
spectacles, like those commonly used by aged persons, are 
simple microscopes. Magnifying glasses, mounted in 
frames such as are for sale by opticians and others, for 
the detection of counterfeit money, are simple microscopes, 
and are useful in studying the coarser structure of plants 
and animals. 

5. The most powerful simple microscopes are made by 
melting in a flame a thread of spun glass, so as to form a 



4. Kinds of microscope ? What are simple microscopes ? 
5* Construction of the most powerful simple microscopes? In practice? 
doublet ? Triplet ? Why are compound microscopes superior to simple ones ? 



238 THE MICROSCOPE. 



minute globule or bead, which, when set in a piece of 
metal and used to examine objects on a plate of glass held 
up to the light, gives a high magnifying power. In prac- 
tice, however, it is found better to use several magnifying 
glasses of moderate power, than a simple lens alone of 
high power. A combination of two lenses is called a dou b- 
let — of three, a triplet. All simple microscopes throw an 
enlarged image of the object upon the retina. Compound 
microscopes are so constructed that the enlarged image of 
an object is again magnified by a second lens, and hence 
their magnifying power is vastly superior to that of simple 
microscopes. 

6. The accompanying diagrams will explain the action 
of the compound microscope compared with that of the 




Fig. 58.— Simple Microscope. 

simple microscope. In Fig. 58, which represents the work- 
ing of the simple microscope, the rays from the object (a I), 
passing through the lens (l), form an image {a' V) in the 
retina of the eye (e), and as all images are inverted in the 
eye, the object is seen as all other objects are, and appears 
erect. In Fig. 59 is seen the action of the compound 
microscope. An inverted image {a' h') of the object {a I) 
is magnified by the second lens (l/), and an erect image is 
thrown upon the retina, which, as all other objects seen 
erect with the naked eye are inverted, gives to the image 
a contrary direction, or inverts it to the mind. 

6. Explain, by means of the diagram, the action of the compound microscope. 



THE MICROSCOPE. 



239 



7. A Compound Microscope consists of two por- 
tions : the optical portion, or the lenses, and the mechanical 
portion, or the instrument which bears # jj»^»» k 
the lenses. The glasses of a compound 
microscope are two : the object-glass (d), 
Fig. 60, and the lower lens of Fig. 59, 
and the ocular or eye-piece (a), Fig. 60, 
and the upper piece of Fig. 59. Both 
the object-glass and the eye-piece may, 
and usually do, consist of more than 
one lens, for, as previously mentioned, 
better results are obtained by a com- 
bination of lenses of moderate power 
than by single lenses of high power 
and great curvature. 

8. How to choose and use a 
Microscope. — No attractiveness in 
the mechanical part of a microscope 
can compensate for inferior lenses; 
and the very first consideration in the 
choice of an instrument should be the 
excellence of the optical part of the 
instrument. In the use of the instru- 
ment, care should be exercised to keep 
the lenses clean, free from dust, not to 
press the object-glass upon the object 
under observation, and not to wet it 
in the water in which most objects are 
examined. A good microscope re- 
quires its own table ; and when not 
in use, should be covered by a bell 
glass or a clean linen cloth. 

9. The mechanical portion of the instrument varies 



Jiii^^ 




Fig. 59. 
Compound Microscope. 



7. Portions, in a compound microscope ? The glasses ? 

8. How to choose a microscope ? How to use it? 

9. The characteristics of the best instrument? What special requisites should 
be insisted upon ? Why, as to a horizontal stage ? 



240 



THE MICROSCOPE. 



greatly in different instruments. That one is the best 
which is simplest, the most solid and easily managed. 
The stage (e), upon which the object is placed, should 




A, Eye-piece. 

B, Body. 

C, Collar. 

D, Object-glass. 



not be movable : it should be solid and firm. The 
screw by which the focal distance is adjusted, and which 



THE MICROSCOPE. 



241 



is in constant nse, should be so placed that it can be 
worked by the hand resting on the table: otherwise fa- 




PlG. 61. 

tigue is soon induced. The direction of the tube carry- 
11 



242 THE MICROSCOPE. 

ing the glasses should be perpendicular, and the stage 
therefore horizontal. Most objects in human anatomy are 
examined in water or in other liquids, or they are them- 
selves liquids; hence an oblique stage is often incon- 
venient. 

10. Additional Apparatus. — As almost all objects 
in human anatomy are examined by transmitted light 
thrown up from the mirror (g, Fig. 60) beneath the stage 
through the object to the eye, they must be placed upon 
strips* of clear glass about three inches long and one inch 
wide, commonly called "slides." These should be pro- 
cured with the microscope. Again, most objects seen with 
high powers require to be covered with a thin plate of 
glass, very properly called a " cover," that the moisture of 
the specimen may not tarnish the object-glass. Square or 
circular covers of very thin glass are therefore provided ; 
and a good supply of these should be always on hand. 
These glasses should be kept in a covered dish filled with 
a mixture of alcohol and water. Simple water will not re- 
move the fatty matter which exists in all animal tissues, 
and, therefore, the glasses cannot be thoroughly cleaned 
with it alone. 

11. When glasses are required for use, they should be 
removed from the liquid and wiped clean and dry with a 
soft linen handkerchief. Delicate knives, scissors, needles 
mounted in handles, forceps, pipettes or little tubes for 
taking up water, should be obtained ; these are essential to 
all microscopical study. The table should be supplied with 
glass-stoppered bottles containing the various liquids or- 
dinarily used in the study of physiology. Thus, tincture 
of iodine is indispensable in studying vegetable structure, 
acetic acid in the study of animal tissues ; and other articles 
will have to be added from time to time, as your progress 
in study demands them. 

10. Slides ? Covers, square and circular? How kept? 

1 1 . Cleaning the glasses ? Knives, scissors, etc. ? Various liquids ? 



THE MICKOSCOPE. 243 



12. Preliminary Studies. — In order to prepare the 
way for the study of any department of science with the 
aid of the microscope — for the microscope is but an eye, and 
can be turned in almost any direction for purposes of in- 
vestigation — it is necessary to become acquainted with the 
many objects which are liable to complicate the examina- 
tion of particular structures. Both air and water are full 
of floating bodies, and the most common of these should 
first occupy the attention. In the city, particles of starch 
are always floating in the air. Take a very minute portion 
of wheat flour, place it in the middle of a clean glass " slide," 
drop upon it a drop of pure water, coyer it with a plate 
of thin glass, and examine it with a power of from one 
hundred to six hundred diameters. It will be found to be 
composed of minute grains or granules, the largest of which 
are made up of coats or layers, like an onion, arranged 
around a central spot called the liilum. 

13. Make another preparation in the same manner, and, 
after adding the water and before covering with the thin 
glass cover, add a small drop of a solution of iodine. 
Now, upon examining the specimen, every grain will be 
seen to be of a beautiful deep blue color. After thus 
studying wheat starch, the starch of Indian corn, of arrow- 
root, and of various grains should be examined in like man- 
ner, and their resemblances and differences noted. The 
granules of potato-starch are as distinctly paarked as any. 
(See Fig. 15, page 61.) 

14. Fibres of cotton, lint, and wool are liable to be 
found in every specimen prepared for microscopical exami- 
nation. In order to study these, any cotton, woollen, or 
linen fabric, or garment, may be scraped, and the scrap- 
ings placed on a piece of glass moistened with water, cov- 
ered with the thin glass plate or cover as before, and exam- 

1 2. Bodies, in air and water ? The examination of starch ? 

13. The examination with solution of iodine ? Advice respecting other arti- 
cles ? 

1 4. Directions for examining cotton and other fibres 1 Vegetable hairs ? 



244 THE MICROSCOPE. 



ined with the same magnifying power, namely, from one 
hundred to six hundred diameters. Vegetable hairs or 
down are constantly floating in air and water. These are 
of very various forms, are simple or grouped, and form 
very interesting objects of study. They are readily pro- 
cured from the epidermis or outer membrane of the leaves 
or stems of plants, by section with a delicate knife. 

15. The tissues of plants, epidermis, ducts, and woody 
fibres are constantly found in microscopic preparations. 
They may be studied in delicate sections made with 
a sharp knife, or by tearing vegetable tissues apart with 
needles. The down of moths, the hairs of different- 
animals, the fibres of paper, the most common animal- 
cules in water, the dust of shelves, and generally the 
structures found in all vegetable and animal substances 
by which we are surrounded, should be studied as a pre- 
liminary to any special line of microscopical investiga- 
tion. 

16. The Study of Human Tissues. — When this has 
been done and familiarity with the use of the instrument 
has been obtained, proceed to the study of the human 
body, for human physiology is our subject. If the end of 
the finger be pricked with a pin, a drop of blood may be 
procured for examination. Place this on one of the glass 
slides, cover it with a thin piece of glass, press down the 
cover so as to make a thin layer, and then examine with 
the magnifying power just mentioned. Do not add water, 
for that will cause the blood corpuscles to disappear. If 
the drop of blood is placed under the microscope at once 
after being drawn from the finger, most interesting phe- 
nomena will be observed. The red corpuscles will be seen 
to arrange themselves in rows, like piles of coin, while the 
blood is coagulating. The spherical, white corpuscles will 

15. Directions for examining various tissues? Down of moths, and other 
structures ? 

1 6. Directions for examining a drop of blood ? 



THE MICROSCOPE. 245 



be left out of the rows of red disks, and, if the highest 
power be used, will be seen to change their shape con- 
stantly. 

17. If you scrape with a dull knife the inside of the 
cheek, the flattened scales of " pavement epithelium," or 
of the insensible covering which, analogous to the scarf- 
skin on the outer surface of the body, lines the cavities of 
its interior, may be readily studied. They have the appear- 
ance of transparent tiles, each enclosing a round or oval 
body, called its nucleus. Dandruff and the scrapings 
from the skin of the body are composed of scales like 
those of the mouth, but they differ somewhat in being 
hardened by horny matter, and in having a very faint 
central body or nucleus. 

18. The Tissues of the Inferior Animals.— The 
warm-blooded animals do not differ in the tissues, or mi- 
croscopic structures, that compose them, but only in the 
amount and arrangement of these tissues. Milne Edwards 
says these tissues " do not differ much in different animals, 
but their mode of association varies ; and it is chiefly by 
reason of the differences in the combination of these asso- 
ciations in various degrees, that each species possesses the 
anatomical properties and characters which are peculiar 
to it." 

19. Hence the butcher's stall will furnish all the mate- 
rials for the study of the microscopic tissues. The struc- 
ture of the heart, lungs, liver, brain, and muscle may all 
be studied, and well studied, by using minute pieces of 
the flesh of the lower animals, especially of the quadru- 
peds. Such portions of these animals as are not exposed 
for sale can be readily obtained by order from the slaugh- 
ter-house. To examine with the powers of which we 
have been speaking, it is only necessary to cut off exceed- 

1 7. Examination of the scales of the mouth ? Dandruff ? 

18. In what as respects the tissues, do the warm blooded animals differ? 
btatement of Milne Edwards ? 

1 9. How to procure materials for the study of the tissues of man ? 



246 THE MICROSCOPE. 



ingly small pieces, tear them apart with needles, or make 
very delicate sections with a sharp knife. 

20. Incentives to Study. — A complete knowledge of 
all minute structures is not to be expected at once, for you 
are here introduced into a new realm of Nature, a world 
of little things as vast, as wonderful, and as carefully con- 
structed as the starry firmament, — that other realm of 
grand objects which the astronomer nightly scans with the 
telescope. It will not appear singular, therefore, if, at first, 
you feel strange and awkward in this new creation. With a 
little perseverance, however, and with the attention directed 
toward simple objects at the outset, it will not be long be- 
fore an increasing experience will engender confidence. 

21. If to all this there be added an enthusiastic study of 
the standard authorities on the subject, the rate of progress 
will be by so much the more rapid. As compared with 
similar studies, few possess more interest than microscopy, 
and to the one who pursues it with fondness, it constantly 
affords sources of pleasure and agreeable surprises ; and in 
the end, often leads to new and valuable additions to the 
sum of human knowledge. The depths which the micro- 
scope is employed to fathom are no more completely known, 
than are the heights above us explored and comprehended 
by the astronomer. 



QUESTIONS FOR TOPICAL REVIEW. 
State what you can on the following subjects : 



1. Voice and speech 227, 228 

2. The organ of the voice 228, 229 

3. The vocal cords 230, 231 

4. The production of the voice.232, 233 

5. The varieties of voice 233, 234 

6. Ventriloquism 235 

7. The law of the tissues 236 



8. Necessity of the microscope . . . 236 

9. Convex lenses 236, 237 

10. Kinds of microscope 237, 238 

11. Choosing a microscope 239, 242 

12. Preliminary studies 243, 244 

13. The study of human tissues 244 

14. The study of the inferior animals 245 



APPENDIX. 



POISONS AND THEIR ANTIDOTES. 

Accidents from poisoning are of such frequent occurrence, that 
every one should be able to administer the more common antidotes, 
until the services of a physician can be obtained. As many poisons 
bear a close resemblance to articles in common use, no dangerous 
substance should be brought into the household without having the 
word poison plainly written or printed on the label ; and any pack- 
age, box, or vial, without a label, should be at once destroyed, if the 
contents are not positively known. 

When a healthy person is taken severely and suddenly ill soon 
after some substance has been swallowed, we may suspect that he has 
been poisoned. In all cases where poison has been taken into the 
stomach, it should be quickly and thoroughly evacuated by some 
active emetic, which can be speedily obtained. This may be accom- 
plished by drinking a tumblerful of warm water, containing either a 
tablespoonful of powdered mustard or of common salt, or two tea- 
spoonruls of powdered alum in two tablespoonfuls of -syrup. When 
vomiting has already taken place, it should be maintained by copious 
draughts of warm water or mucilaginous drinks, such as gum-water 
or flaxseed tea, and tickling the throat with the finger until there is 
reason to believe that all the poisonous substance remaining in the 
stomach has been expelled. 

The following list embraces only the more common poisons, to- 
gether with such antidotes as are usually at hand, to be used until 
the physician arrives. 

POISONS. 

Acids. — Hydrochloric acid; muriatic acid (spirits of salt); nitric 
acid (aqua fortis) ; sulphuric acid (oil of vitriol). 

Antidote. — An antidote should be given at once to neutralize the 
acid. Strong soapsuds is an efficient remedy, and can always be 
obtained. It should be followed by copious draughts of warm water 
or flaxseed tea. Chalk, magnesia, soda or saleratus (with water) or 



248 APPENDIX. 

lime-water, are the best remedies. When sulphuric acid has been 
taken, water should be given sparingly, because, when water unites 
with this acid, intense heat is produced. 

Oxalic acid. 

Antidote. — Oxalic acid resembles Epsom salts in appearance, and 
may easily be mistaken for it The antidotes are magnesia, or chalk 
mixed with water. 

Prussic Acid; oil of bitter abnonds ; laurel water; cyanide of potas- 
sium (used in electrotyping). 

Antidote. — Cold douche to the spine. Chlorine water, or water 
of ammonia largely diluted, should be given, and the vapor arising 
from them may be inhaled. 

Alkalies and their Salts. — Ammonia (hartshorn), liquor or water 
of ammonia. Potassa : — caustic potash, strong ley, carbonate ofpotassa 
(pearlash), nitrate ofpotassa (saltpetre). 

Antidote. — Give the vegetable acids diluted, as weak vinegar ; 
acetic, citric, or tartaric acids dissolved in water. Castor oil, linseed oil, 
and sweet oil may also be used ; they form soaps when mixed with the 
free alkalies, which they thus render harmless. The poisonous effects 
of saltpetre must be counteracted by taking mucilaginous drinks 
freely, so as to produce vomiting. 

Alcohol.. — Brandy, wine; all spiritvx>us liquors. 

Antidote. — Give as an emetic ground mustard or tartar emetic. If 
the patient cannot swallow, introduce a stomach pump ; pour cold 
water on the head. 

Gases. — Chlorine, carbonic acid gas, carbonic oxide, fumes of burning 
charcoal, sulphuretted hydrogen, illuminating or coal-gas. 

Antidote. — For poisoning by chlorine, inhale, cautiously, ammonia 
(hartshorn). For the other gases, cold water should be poured upon 
the head, and stimulants cautiously administered ; artificial respira- 
tion. (See Marsliall HaWs Beady Method, page 250.) 

Metals. — Antimony, tartar emetic, wine of antimony, etc. 

Antidote. — If vomiting has not occurred, it should be produced by 
tickling the throat with the finger or a feather, and the abundant use 
of warm water. Astringent infusions, such as common tea, oak bark, 
and solution of tannin, act as antidotes. 

Arsenic. — White arsenic, Fowler's solution, fly-powder, cobalt, Paris 
green, etc. 

Antidote. — Produce vomiting at once with a tablespoonful or two 
of powdered mustard in a glass of warm water, or with ipecac. The 
antidote is hydrated peroxide of iron. If Fowler's solution has been 
taken, lime-water must be given. 



APPENDIX. 249 



Copper. — Acetate of copper (verdigris), sulphate of copper (blue 
vitriol), food cooked in dirty copper vessels, or pickles made green 
by copper. 

Antidote. — Milk or white of eggs, with mucilaginous drinks (flax- 
seed tea, etc.), should be freely given. 

Iron. — Sulphate of iron (copperas), etc. 

Antidote. — Carbonate of soda in some, mucilaginous drink, or in 
water, is an excellent antidote. 

Lead. — Acetate of lead (sugar of lead), carbonate of lead (white 
lead), water kept in leaden pipes or vessels, food cooked in vessels 
glazed with lead. 

Antidote. — Induce vomiting with ground mustard or common 
salt in warm water. The antidote for soluble preparations of lead is 
Epsom salts ; for the insoluble forms, sulphuric acid largely diluted. 

Mercury. — Bichloride of mercury (corrosive sublimate), ammoniated 
mercury (white precipitate), red oxide of mercury (red precipitate), red 
8ulp7iuret of mercury (vermilion). 

Antidote. — The white of eggs, or wheat flour beaten up with 
water and milk, are the best antidotes. 

Silver. — Nitrate of silver (lunar caustic). 

Antidote. — Give a teaspoonful of common salt in a tumbler of 
water. It decomposes the salts of silver and destroys their activity. 

Zinc. — Sulpliate of zinc, etc. (white vitriol). 

Antidote.— The vomiting may be relieved by copious draughts 
of warm water. The antidote is carbonate of soda administered in 
water. 

Narcotic Poisons. — Opium (laudanum, paregoric, salts of mor- 
phia, Godfrey's cordial, Dalby's carminative, soothing syrup, cholera 
mixtures), aconite, belladonna, hemlock, stramonium, digitalis, tobacco, 
hyosciamus, nux vomica, strychnine. 

Antidote. — Evacuate the stomach by the most active emetics, as 
mustard, alum, or sulphate of zinc. The patient should be kept in 
motion, and cold water dashed on the head and shoulders. Strong 
coffee must be given. The physician will use the stomach pump and 
electricity. In poisoning by nux vomica or strychnine, etc., chloro- 
form or ether should be inhaled to quiet the spasms. 

Irritant Vegetable Poisons, — Croton oil, oil of savine, poke, oil of 
tansy, etc. 

Antidote — If vomiting has taken place, it may be rendered easier 
by copious draughts of wann water. But if symptoms of insensibility 
have come on without vomiting, it ought to be immediately excited by 
ground mustard mixed with warm water, or some other active emetic; 

11* 



250 APPENDIX. 

and after its operation an active purgative should be given. After 
evacuating as much of the poison as possible, strong coffee or vinegar 
and water may be given with advantage. 

Poisonous Fish. — Conger eel, mussels, crabs, etc. 

Antidote. — Evacuate, as soon as possible, the contents of the stom- 
ach and bowels by emetics (ground mustard mixed with warm water 
or powdered alum), and castor oil, drinking freely at the same time 
of vinegar and water. Ether, with a few drops of laudanum mixed 
with sugar and water, may afterward be taken freely. 

Poisonous Serpents. — Antidote. — A ligature or handkerchief 
should be applied moderately tight above the bite, and a cupping-glass 
over the wound. The patient should drink freely of alcoholic stim- 
ulants containing a small quantity of ammonia. The physician may 
inject ammonia into the veins. 

Poisonous Insects. — Stings of scorpion, hornet, wasp, bee, etc. 

Antidote. — A piece of rag moistened with a solution of carbolic 
acid may be kept on the affected part until the pain is relieved ; and 
a few drops of carbolic acid may be given frequently in a little 
water. The sting may be removed by making strong pressure 
around it with the barrel of a small watch-key. 



DROWNING. 

Marshall Hall's " Ready Method" of treatment in asphyxia 
from drowning, chloroform, coal gas, etc. 

1st. Treat the patient instantly on the spot, in the open air, freely 
exposing the face, neck, and chest to the breeze, except in severe 
weather. 

2d. In order to clear the throat, place the patient gently on the face, 
with one wrist under the forehead, that all fluid, and the tongue itself, 
may fall forward, and leave the entrance into the windpipe free. 

3d. To excite respiration, turn the patient slightly on his side, and 
apply some irritating or stimulating agent to the nostrils, as vera- 
trine, dilute ammonia, etc. 

4th. Make the face warm by brisk friction ; then dash cold water 
upon it. 

5th. If not successful, lose no time ; but, to imitate respiration, 
place the patient on his face, and turn the body gently, but completely 
on the side, and a little beyond ; then again on the face, and so on, al- 
ternately. Repeat these movements, deliberately and perseveringly, 



APPENDIX. 251 



fifteen times only in a minute. (When the patient lies on the thorax, 
this cavity is compressed by the weight of the body, and aspiration 
takes place. When he is turned on the side, this pressure is removed, 
and inspiration occurs.) * 

6th. When the prone position is resumed, make a uniform and 
efficient pressure along the spine, removing the pressure immediately, 
before rotation on the side. (The pressure augments the orpiration ; 
the rotation commences inspiration.) Continue these measures. 

7th. Rub the limbs upward, with firm pressure and with energy. 
(The object being to aid the return of venous blood to the heart.) 

8th. Substitute for the patient's wet clothing, if possible, such 
other covering as can be instantly procured, each bystander sup- 
plying a coat or cloak, etc. Meantime, and from time to time, to 
excite inspiration, let the surface of the body be slapped briskly with 
the hand. 

9th. Rub the body briskly till it is dry and warm, then dash cold 
water upon it, and repeat the rubbing. 

Avoid the immediate removal of the patient, as it involves a 
dangerous loss of time — also, the use of bellows, or any forcing instru- 
ment ; also, the warm bath, and aU rough treatment. 



GLOSSARY. 



Ab-do'men (Latin abdo, to conceal). The largest cavity of the body, 
containing the liver, stomach, intestines, etc.; the belly. 

Ab-sor'bents (L. ab and sorbeo, to suck up). The vessels which take 
part in the process of absorption. 

Ab-sorp'tion. The process of sucking up fluids by means of an 
animal membrane. 

Ac-co^-mo-da'tion of the Eye. The alteration in the shape of the 
crystalline lens, which accommodates or adjusts the eye for near 
and remote vision. 

Ac'id, Lactic (L. lac, milk). The acid ingredient of sour milk ; the 
gastric juice also contains it. 

Al-bu'men, or Albumin (L. albus, white). An animal substance re- 
sembling white of egg. 

Al-bu'mi-nose (from albumen). A soluble animal substance pro- 
duced in the stomach by the digestion of the albuminoid sub- 
stances. 

AL-Bu'MiN-orD substances. A class of proximate principles resembling 
albumen ; they may be derived from either the animal or vegetable 
kingdoms. 

Al'i-ment (L. alo, to nourish). That which affords nourishment ; 
food. 

Al-i-ment'a-ry Ca-nal (from aliment). A long tube in which the 
food is digested, or prepared for reception into the system. 

An-^es-thet'ics (Greek, ocv, an, without, ai6^rj6ia, aisthesia, feel- 
ing). — Those medicinal agents which prevent the feeling of pain, 
such as chloroform, laughing-gas, etc. 

An-i-mai/cule (L. animal' culum, a small animal). Applied to an- 
imals which can only be seen with the aid of the microscope. Ani- 
malculum (plural, animalcula) is used with the same meaning. 

A-or'ta (Gr. dopriofioa, aorteomai, to be lifted up). The largest 
artery of the body, and main trunk of all the arteries. It arises from 
the left ventricle of the heart. The name was first applied to the 
two large branches of the trachea, which appear to be lifted up by 
the heart 



GLOSSARY. 253 



A'que-ous Humor (L. aqua, water). A few drops of watery color- 
less fluid occupying the space between the cornea and crystalline 
lens. 

A-rach'noid Mem'brane (Gr. dpcixvri, arachne, a cobweb, and 
eid oS, eidos, like). An extremely thin covering of the brain and 
spinal cord. It lies between the dura mater and the pia mater. 

Ar'bor Vi'tm (L.). Literally, " the tree of life ;" a name given to the 
peculiar appearance presented by a section of the cerebellum. 

Ar'ter-y (Gr. dijp, aer, air, and rijpsiv, terein, to contain). A 
vessel by which blood is conveyed away from the heart. It was 
supposed by the ancients to contain air ; hence the name. 

Ar-tic-u-la'tion (L. articulo, to form a joint). The more or less 
movable union of bones, etc. ; a joint. 

A-ryt'e-noid Car'tt-la-ges (Gr. dpvraiva, arutaina, a pitcher). 
Two small cartilages of the larynx, resembling the mouth of a 
pitcher. 

As-sim-i-la'tion (L. ad, to, and similis, like). The conversion of food 
into living tissue. 

Atj-di'tion (L. audio, to hear). The act of hearing sounds. 

Au'di-to-ry Nerve. One of the cranial nerves; it is the special 
nerve of hearing. 

Au'ri-cle (L. auris, the ear). A cavity of the heart. 

Bar'i-tone (Gr. fiapvS, barus, heavy, and rdvoS, tonos, tone). A 
variety ofmale voice between the bass and tenor. 

Bel-la-don'na (It. beautiful lady). A vegetable narcotic poison. It 
has the property of enlarging the pupil, and thus increasing the 
brilliancy of the eye ; so called from its use by Italian ladies. 

Bi-cus'pid (L. hi, two, and cuspis, prominence). The name of the 
fourth and fifth teeth on each side of the jaw ; possessing two prom- 
inences. 

Bile. The gall, or peculiar secretion of the liver ; a viscid, yellowish 
fluid, and very bitter to the taste. 

Bronch'i (Gr. fipoyxot, bronkos, the windpipe). The two first 
divisions or branches of the trachea; one enters each lung. 

Bronch'i-al Tubes. The smaller branches of the trachea within 
the substance of the lungs, terminating in the air-cells. 

Bronch-i'tis (from bronchia, and itis, a suffix signifying inflamma- 
tion). An inflammation of the larger bronchial tubes ; a " cold" 
affecting the lungs. 
Cal-ca're-ous (L. calx, lime). Containing lime. 
Ca-nai/ (L.). In the body, any tube or passage. 
Ca-ntne' (L. cards, a dog). Name given to the third tooth on each. 



254 GLOSSARY. 

side of the jaw ; in the upper jaw it is also known as the eye-tooth; 
pointed like the tusks of a dog. 

Cap'il-la-ry (L. capil'lus, a hair, capillafris hair-like). The name of 
the extremely minute blood-vessels which connect the arteries with 
the veins. 

Car' bon Diox-ide (CO«). Chemical name for carbonic acid gas. 

Car-bon'ic A-ctd. The gas which is present in the air expired from 
the lungs ; a waste product of the animal kingdom, and a food of 
the vegetable kingdom. 

Car/di-ac (Gr. napSia, cardia, the heart). The cardiac orifice of 
the stomach is the upper one, and is near the heart ; hence its 
name. 

Car-niv'o-rous (L. ca'ro, flesh, and do' ro, to devour). Subsisting 
upon flesh. 

Ca-rot'id Ar-te-ry. The large artery of the neck, supplying the 
head and brain. 

Car'ti-lage. A solid but flexible material, forming a part of the 
joints, air-passages, nostrils, etc. ; gristle. 

Ca'se-lne (L. ca'seus, cheese). The albuminoid substance of milk ; 
it forms the basis of cheese. 

Cer-e-bel'lum (diminutive for cer'ebrum, the brain). The little brain, 
situated beneath the posterior third of the cerebrum. 

Ceb'e-brum (L.). The brain proper, occupying the entire upper por- 
tion of the skull. It is nearly divided into two equal parts, called 
" hemispheres," by a cleft extending from before backward. 

Cho'rold (Gr. xoft lov > chorion, a membrane or covering). The mid- 
dle tunic or coat of the eyeball. 

Chyle (Gr. ;£i>A.dS, chulos, juice). The milk-like fluid formed by the 
digestion of fatty articles of food in the intestines. 

Chyme (Gr. ^Ujuo?, chumos, juice). The pulpy liquid formed by 
digestion within the stomach. 

Cn/i-A (pi. of cil'i-um, an eyelash). Minute, vibratile, hair-like pro- 
cesses found upon the cells of the air-passages, and other parts that 
are habitually moist. 

Cir-cu-la'tion (L. cir' cuius, a ring). The circuit, or course of the 
blood through the blood-vessels of the body, from the heart to the 
arteries, through the capillaries into the veins, and from the veins 
back to the heart. 

Co-ag-u-la'tion (L. coag'ulo, to curdle). Applied to the process by 
which the blood clots or solidifies. 

Coch'le-a (L. coch'lea, a snail-shell). The spiral cavity of the in- 
ternal ear. 



GLOSSARY. 255 



Conch'a (Gr. noyxVi ^onche, a mussel-shell). The external shell- 
shaped portion of the external ear. 

Con-junc-ti'va (L. con and jun'go, to join together). A thin layer 
of mucous membrane which lines the eyelids and covers the front 
of the eyeball ; thus joining the latter to the lids. 

Con-trac-til'i-ty (L. con and tra'ho, to draw together). The prop- 
erty of a muscle which enables it to contract, or draw its extrem- 
ities closer together. 

Con-vo-lu'tions (L. con and vol'vo, to roll together). The tortuous 
foldings of the extenal surface of the brain. 

Con-vui/sion (L. convel'lo, to pull together). A more or less violent 
agitation of the limbs or body. 

Cor'ne-a (L. cor'nu, a horn). The transparent, horn-like substance 
which covers the anterior fifth of the eyeball. 

Cor'pus-cles, Blood (L. dim. of cor' pus, a body). The small bicon- 
cave disks which give to the blood its red color ; the white cor- 
puscles are globular and larger. 

Cos-met'ic (Gt. KodjLisGOjkosmeo, to adorn). Beautifying; applied 
to articles which are supposed to increase the beauty of the 
skin, etc. 

Cra'ni-al (L. cra'nium, the skull). Pertaining to the skull. The 
nerves which arise from the brain are called cranial nerves. 

Cri'coid (Gr. npixoi, kri'kos, a ring). A cartilage of the larynx, 
resembling a seal-ring in shape. 

Crys'tal-line Lens (L. crystal'lum, a crystal). One of the so-called 
humors of the eye ; a double convex body situated in the front part 
of the eyeball. 

Cu'ti-cle (L. dim. ofcu'tis, the skin). The scarf-skin ; also called 
the epider'mis. 

Cu'tis (Gr. dtcvroS, skutos, a skin or hide). The true skin, lying 
beneath the cuticle ; also called the der'ma. 

De-cus-sa'tion (L. decus'sis, the Boman numeral ten, X). A re- 
ciprocal crossing of fibres from side to side. 

Di'a-phragm (Gr. diacppaddoo, diaphrasso, to divide by a partition). 
A large, thin muscle which separates the cavity of the chest from 
the abdomen ; a muscle of respiration. 

Dif-fus'ion op Gases. The power of gases to become intimately 
mingled, without reference to the force of gravity. 

Duct (L. du'co, to lead). A narrow tube ; the thoracic duct is the 
main trunk of the absorbent vessels. 

Du-o-de'num (L. duode'ni, twelve). The first division of the small 
intestines, about twelve fingers-breadth long. 



256 GLOSS AKY. 



Du'ra Ma'ter (L.). Literally, the hard mother ; the tough membrane 
which envelops the brain. 

Dys-pep'si-a (Gt. 8vi, dus, difficult, and itaitzGo, pep' to, to digest). Dif- 
ficult or painful digestion ; a disordered condition of the stomach. 

E-mul'sion (L. emul'geo, to milk). Oil in a finely divided state sus- 
pended in water. 

En-am'el (Fr. email). The dense material which covers the crown 
of the tooth. 

En'er-gy, Specific, of a Nerve. When a nerve of special sense is 
excited, whatever be the cause, the sensation experienced is that 
peculiar to the nerve ; this is said to be the law of the specific 
energy of the nerves. 

Ep-i-glot'tts (Gr. kiti, epi, upon, and yXGorrii, glottis, the entrance 
to the windpipe). A leaf-shaped piece of cartilage which covers 
the top of the larynx during the act of swallowing. 

Ex-cre'tion (L. excer'no, to separate). The separation from the blood 
of the waste particles of the body ; also the materials excreted. 

Ex-pi-ra'tion (L. expi'ro, to breathe out). The act of forcing air out 
of the lungs. 

Ex-ten'sion (L. ex, out, and ten' do, to stretch). The act of restoring a 
limb, etc., to its natural position after it has been flexed, or bent ; 
the opposite of Flexion. 

Fe-nes'tra (L.). Literally, a window ; the opening between the 
middle and internal ear. 

Fi'brin (L. fi'bra, a fibre). An albuminoid substance found in the 
blood ; in coagulating it assumes a fibrous form. 

Flex'ion (L. flee' to, to bend). The act of bending a limb, etc. 

Foi/li-cle (L. dim. otfol'lis, a bag). A little pouch or depression in a 
membrane ; it has generally a secretory function. 

Fun'gous Growths (L. fun'gus, a mushroom). A low grade of vege- 
table life. 

Gan'gli-on (Gr. yayyXiov, ganglion, a knot). A knot-like swell- 
ing in the course of a nerve ; a smaller nerve-centre. 

Gas'tric (Gr. yadrrfp, gaster, stomach). Pertaining to the stomach. 

Gland (L. glans, an acorn). An organ consisting of follicles and 
ducts, with numerous blood-vessels interwoven ; it separates some 
particular fluid from the blood. 

Glos'so-phar-yn-ge'al Nerve {Gr. yA.gd<56(x, glossa, the tongue, and 
<papvyq, pharunx, the throat). The nerve of taste supplying the 
posterior third of the tongue; it also supplies the throat. 

Glu'ten (L.). Literally, glue ; the glutinous albuminoid ingredient 
of wheat. 



GLOSSAEY. 257 

Gran'ule (L. dim. of gra'num, a grain). A little grain ; a micro- 
scopic object. 
Gus-ta'tion (L. gus'to, to taste). The sense of taste. 
Gus'ta-to-ry Nerve. The nerve of taste supplying the front part 

of the tongue; a branch of the " fifth" pair. 
ILem'or-rhage \Qy. aijua, hai'ma, blood, and pijyvvjui, regnumi, 

to burst). Bleeding, or the loss of blood. 
Hem-i-ple'gia (Gr. r/ui6v<z, hemisus, half, and 7tA.jjd6G0, plesso, to 

strike). Paralysis, or loss of power, affecting one side of the body. 
Hem'i-spheres (Gr. 6q>a7pa> sphaira, a sphere). Halt a sphere, the 

lateral halves of the cerebrum, or brain proper. 
He-pat'ic (Gr. r/7tap, Tiepar, the liver). Pertaining to the liver. 
Her-biv'o-rous (L. Jier'ba, an herb, and vo'ro to devour). Applied 

to animals that subsist upon vegetable food. 
Hu'mor (L.). Moisture : the humors are transparent contents of the 

eyeball. 
Hy-dro-pho'bi-a (Gr. vdop, hudor, water, and <po(3sao, phobeo, to 

fear). A disease caused by the bite of a rabid dog or other animal. 

In a person affected with it, convulsions are occasioned by the sight 

of a glittering object, like water, by the sound of running water, 

and by almost any external impression. 
Hy'gi-ene (Gr. vyieia, huygieia, health). The art of preserving 

health and preventing disease. 
Hy'per-o-pi-a. Abbreviated from Hy'per-met-ro'pi-a (Gr. vitep, 

huper, beyond, /uerpov, metron, the measure, and ooi}), ops, the eye). 

A defect of vision dependent upon a too short eyeball ; so called 

because the rays of light are brought to a focus at a point behind 

the retina ; the true " far sight." 
In-ci'sor (L. inci'do, to cut). Applied to the four front teeth of both 

jaws, which have sharp cutting edges. 
In'cus (L). An anvil ; the name of one of the bones of the middle 

ear. 
In-sal-i-va'tion (L. m, and salfva, the fluid of the mouth). The 

mingling of the saliva with the food during the act of chewing. 
In-spi-ra'tion (L. m, and spi'ro, spira'tum, to breathe). The act of 

drawing in the breath. 
In-teg'u-ment (L. in, and te'go, to cover). The skin, or outer covering 

of the body. 
In-tes'tine (L. in'tus, within). The part of the alimentary canal 

which is continuous with the lower end of the stomach ; also called 

the intestines, or the bowels. 
I'ris (L. i'ris, the rainbow). The thin muscular ring which lies be- 



258 GLOSSARY. 

tween the cornea and crystalline lens, and which gives the eye 

its brown, blue, or other color. 
Ju'gu-lar (L.ju'gulum, the throat). The name of the large veins 

which run along the front of the neck. 
Lab'y-rinth (Gr. Xafiijpiv'SoS, laburin'thos, a building with many 

winding passages). The very tortuous cavity of the inner ear, 

comprising the vestibule, semicircular canals, and the cochlea. 
Lach'ry-mal Apparatus (L. lach'ryma, a tear). The organs for 

forming and conveying away the tears. 
Lac'te-als (L. lac, lac'tis,m\\)s). The absorbent vessels of the small 

intestines ; during digestion they are filled with chyle, which has 

a milky appearance. 
La-ryn' go-scope (Gr. Xdpvyf-, larunx, the larynx, and dH07tea>, 

skopeo, to look at). The instrument by which the larynx may be 

examined in the living subject. 
Lar'ynx (Gr.). The cartilaginous tube situated at the top of the 

windpipe, or trachea ; the organ of the voice. 
Lens (L.). Literally, a lentil ; a piece of transparent glass or other sub- 
stance so shaped as either to converge or disperse the rays of light. 
Lig- a-ment (L. li'go, to bind). A strong, fibrous material binding 

bones or other solid parts together; it is especially necessaiy to 

give strength to joints. 
Lig'a-ture. A thread of silk or other material used in tying around 

an artery. 
Lymph (L. lym'pha, spring- water). The colorless, watery fluid con- 
veyed by the lymphatic vessels. 
Lym-phat'ic Vessels. A system of absorbent vessels. 
Mai/le-us (L.). Literally, the mallet ; one of the small bones of the 

middle ear. 
Mar'row. The soft, fatty substance contained in the central cavities 

of the bones : the spinal marrow, however, is composed of nervous 

tissue. 
Mas-ti-ca'tion (L. mas'tico, to chew). The act of cutting and grind- 
ing the food to pieces by means of the teeth. 
Me-dul'la Ob-lon-ga'ta. The Cl oblong marrow," or nervous cord, 

which is continuous with the spinal cord within the skull. 
Mem-bra'na Tym'pan-i (L.). Literally, the membrane of the drum ; 

a delicate partition separating the outer from the middle ear ; it is 

sometimes incorrectly called the drum of the ear. 
Mem'brane. A thin layer of tissue serving to cover some part of 

the body. 
Mi'cro-scope (Gr. juitcpot, mikros, small, and duortSGo, skopeo, to 



GLOSSARY. 259 

look at). An optical instrument which assists in the examination 

of minute objects. 
Mo'lar (L. mo'la, a mill). The name applied to the three back teeth 

of each side of the jaw ; the grinders, or mill-like teeth. 
Mo'tor (L. mo'veo, mo' turn, to move). Causing motion ; the name 

of those nerves which conduct to the muscles the stimulus which 

causes them to contract. 
Mucous Mem'brane. The thin layer of tissue which covers those in- 
ternal cavities or passages which communicate with the external air. 
Mu'cus. The glairy fluid which is secreted by mucous membranes, 

and which serves to keep them in a moist condition. 
My-o'pi-a (Gr. jii'&o, muo, to contract, and aoif), ops, the eye). A de- 
fect of vision dependent upon an eyeball that is too long, rendering 

distant objects indistinct ; near-sight. 
Na'sal (L. na'sus, the nose). Pertaining to the nose ; the nasa* 

cavities contain the distribution of the special nerve of smell. 
Nerve (Gr. vevpov, neuron, a cord or string). A glistening, white 

cord of cylindrical shape, connecting the brain or spinal cord with 

some other organ of the body. 
Nerve Cell. A minute, round and ashen-gray eel 1 found in the 

brain and other nervous centres. 
Nerve Fi'bre. An exceedingly slender thread of nervous tissue 

found in the various nervous organs, but especially in the nerves j 

it is of a white color. 
Nu-tri'tion (L. nu'trio, to nourish). The processes by which the 

nourishment of the body is accomplished. 
(E-soph'a-gus (Gr.). Literally, that which carries food. The tube 

leading from the throat to the stomach ; the gullet. 
O-le-ag'i-nous (L. oleum, oil). Of the nature of oil : applied to an 

important group of food-principles — the fats. 
Ol-fac'to-ry (L. olfa'cio, to smell). Pertaining to the sense of smell 
Oph-thal'mo-scope (Gr. 6cp^aX/j.6i, ophthalmos, the eye, and 6xo~ 

Ttioa, skopeo, to look at). An instrument devised for examining the 

interior of the globe of the eye. 
Op'tic (Gr. ortTGo, opto, to see). Pertaining to the sense of sight. 
Or'bit (L. or'bis, the socket). The bony socket or cavity in which 

the eyeball is situated. 
Os'mose (Gr. God/uoS, osmos, a thrusting or impulsion). The process 

by which liquids are impelled through a moist membrane. 
Os'se-ous (L. os, a bone). Consisting of, or resembling bone. 
Pal' ate (L. polo! turn, the palate). The roof of the mouth, consisting 

of the hard and soft palate. 



260 GLOSSAKY. 



Pai/mar. Relating to the palm of the hand. 

Pan'cre-as (Gr. 7ta$, itavroS, pas, pantos, all, and xpsaS, kreas, 
flesh). A long, flat gland situated near the stomach ; in the lower 
animals the analogous organ is called the sweet-bread. 

Pa-pil'l^e (L. papil'la). The minute prominences in which termi- 
nate the ultimate fibres of the nerves of touch and taste. 

Pa-ral'y-sis. A disease of the nervous system marked by the loss 
of sensation, or voluntary motion, or both ; palsy. 

Par-a-ple'gi-a (Gr. 7tapa7tXi}tidGo, paraplesso, to strike amiss). A 
form of paralysis affecting the lower half of the body. 

Pa-tei/la (L. dim. of pat'ina, a pan). The knee-pan ; a small 
bone. 

Pei/vis (L.). Literally a basin ; the bony cavity at the lower part of 
the trunk. 

Pep'sin (Gr. 7CsitzG0, pepto, to digest). The organic principle of the 
gastric juice. 

PePv-i-stai/tic Move'ments (Gr. 7t8pi6re7iX&), peristello, to contract). 
The slow, wave-like movements of the stomach and intestines. 

Per-i-to-ne'um (Gr. 7tspirEiroo, periteino, to stretch around). The 
investing membrane of the stomach, intestines, and other abdom- 
inal organs. 

Per-spi-ra'tion (L. perspi'ro, to breathe through). The sweat, or 
watery exhalation of the skin ; when visible, it is called sensible 
perspiration, when invisible, it is called insensible perspiration. 

Pe'trous (Gr. Ttirpa, petra, a rock). The name of the hard portion 
of the temporal bone, in which is situated the drum of the ear and 
labyrinth. 

Phar'ynx (Gr. qxxpvy£, pharunx, the throat). The cavity between 
the back of the mouth and gullet. 

Phys-i-ol'o-gy (Gr. q>v6ii, phusis, nature, and XoyoS, logos, a dis- 
course). The science of the functions of living, organized beings. 

Pr*A Ma'ter (L.). Literally, the tender mother ; the innermost of the 
three coverings of the brain. It is thin and delicate ; hence the 
name. 

Pleu'ra (Gr. itXsvpoi, a rib). A membrane covering the lung and 
lining the chest. There is one for each lung. 

Pleu'ri-sy. An inflammation affecting the pleura. 

Pneu-mo-gas'tric (Gr. itvEvnoov, pneumon, the lungs, and yadrrfp, 
gasler, the stomach). The name of a nerve distributed to the lungs 
and stomach ; it is the principal nerve of respiration. 

Pneu-mo'nia (Gr.). An inflammation affecting the air-cells of the 
lungs. 



GLOSSARY. 261 

Pres-by-o'pi-a (Gr. 7tpsd/3vS } presbus, old, and ffity, ops, the eye). 
A defect of the accommodation of the eye, caused by the harden- 
ing of the crystalline lens; the "far-sight" of adults and aged 
persons. 

Process (L. proce'do, processus, to proceed, to go forth). Any pro- 
jection from a surface. Also, a method of performance ; a pro- 
cedure. 

Pty'a-lln (Gr. itrvaXov , ptualon, saliva). The peculiar organic 
ingredient of the saliva. 

Pul'mo-na-ry (L. pul'mo, pulmo'nis, the lungs). Pertaining to the 
lungs. 

Pulse (L. pel'lo, pul'sum, to beat). The striking of an artery against 
the finger, occasioned by the contraction of the heart, commonly 
felt at the wrist. 

PifpiL (L. pupil'la). The central, round opening in the iris, through 
which light passes into the depths of the eye. 

Py-lo'rus (Gr. TtvXoapoiy puloros, a gate-keeper). The lower open- 
ing of the stomach, at the beginning of the small intestine. 

Re'flex Action. An involuntary action of the nervous system, by 
which an external impression conducted by a sensory nerve is 
reflected, or converted into a motor impulse. 

Res-pi-ra'tion (L. res'piro, to breathe frequently). The function 
of breathing, comprising two acts : inspiration, or breathing in, and 
expiration, or breathing out. 

Ret'i-na (L. re'te, a net). The innermost of the three tunics or coats 
of the eyeball, being an expansion of the optic nerve. 

Sac'cra.-rlne (L. sac' charum, sugar). Of the nature of sugar; 
applied to the important group of food substances which embraces 
the different varieties of sugar, starch, and gum. 

Sa-li'va (L.). The moisture or fluids of the mouth, secreted by the 
salivary glands, etc. 

Scle-rot'ic (Gr. tinXrfpoS, skleros, hard). The tough, fibrous outer 
tunic of the eyeball. 

Se-ba'ceous (L. sebum, fat). Resembling fat ; the name of tne oily 
secretion by which the skin is kept flexible and soft. 

Se-cre'tion (L. secer'no, secre'tum, to separate). The process ot 
separating from the blood some essential important fluid ; which 
fluid is also called a secretion. 

Sem-i-cir'cu-lar Canals. A portion of the internal ear. 

Sen-sa'tion. The perception of an external impression by the ner- 
vous system ; a function of the brain. 

Ben-si-bil'i-ty, General. The power possessed by nearly all parts 



262 GLOSSARY. 



of the human body of recognizing the presence of foreign objects 
that come in contact with them. 

Se'rum (L.). The watery constituent of the blood, which separates 
from the clot during the process of coagulation. 

Skel'e-ton (Gr.). The bony framework of an animal, the different 
parts of which are maintained in their proper relative positions. 

Spec'tro-scope (from spec'trum and 6ko%eoo, scopeo, to examine the 
spectrum). An instrument employed in the examination of the 
spectrum of the sun or any other luminous body. 

Sphyg'mo-graph (Gr. <5<pvyix6i, sphugmos, the pulse, and ypacpao, 
grapho, to write). An ingenious instrument by means of which 
the pulse is delineated upon paper. 

Sta'pes (L.). Literally, a stirrup ; one of the small bones of the tym- 
panum, or middle ear, resembling somewhat a stirrup in shape. 

Sym-pa-thet'ic system of Nerves. A double chain of nervous 
ganglia, connected together by numerous small nerves, situated 
chiefly in front of and on each side of the spinal column. 

Syn-o'vi-a (Gr. dvv, sun, and gdoV, oon, resembling an egg). The 
lubricating fluid of joints, so called because it resembles the white 
of egg. 

Sys'to-le (Gr. 6v6teXXqo, sustello, to contract). The contraction of 
the heart, by which the blood is expelled from that organ. 

Tac'tile (L. tac'tus,^ touch). Relating to the sense of touch. 

Tem'po-ral (L. tem'pms, time, and tem'pora, the temples). Pertain- 
ing to the temples ; the name of an artery : so called, because the 
hair begins to turn white with age in that portion of the scalp. 

Tes'dox (L. ten'do, to stretcb). The white, fibrous cord or band by 
which a muscle is attached to a bone ; a sinew. 

Tet'a-nus (Gr. teIvgo, teino, to stretch). A disease marked by per- 
sistent contractions of all or some of the voluntary muscles; 
those of the jaw are sometimes solely affected, the disorder is then 
termed locked-jaw. 

Tho rax (Gr. Scopac, thorax, a breastplate). The upper cavity of 
the trunk of the body, containing the lungs, heart, etc. ; the 
chest. 

Thy'roid (Gr. SvpedS, thureos, a shield). The largest of the carti- 
lages of the larynx; its angular projection in the front of the neck 
is called " Adam's apple." 

Tra'che-a (Gr. rpaxvS, trachus, rough). The windpipe, or the 
largest of the air-passages ; composed in part of cartilaginous 
lings, which render its surface rough and uneven. 

Trans-fu'sion (L. transfun'do, to pour from one vessel to another). 



GLOSSARY. 263 

The operation of injecting blood taken from one person into the 
veins of another ; other fluids than blood are sometimes used. 

Trich-i'na Spi-ra'lis. (L.) A minute species of parasite or worm, 
which infests the flesh of the hog, and which may be introduced 
into the human system by eating pork not thoroughly cooked. 

Tym'pa-num (Gr. rvjurtavor, tumpanon, a drum). The cavity of 
the middle ear, resembling a drum in being closed by two mem- 
branes, and in having communication with the atmosphere. 

U'vu-la (L. uva, a grape). The small pendulous body attached to 
the back part of the palate. 

Vas'cu-lar (L. vas'culum, a little vessel). Pertaining to, or contain- 
ing blood-vessels. 

Ve'nous (L. ve'na, a vein). Pertaining to, or contained within a 
vein. 

Ven-ti-la'tion. The introduction of fresh ah* into a room or build- 
ing, in such a manner as to keep the air within it in a pure condi- 
tion. 

Ven-tril'o-quism (L. ven'ter, the belly, and lo'quor, to speak). A 
modification of natural speech by which the voice is made to 
appear to come from a distance. The ancients supposed that the 
voice was formed in the belly ; hence the name. 

Ven'tri-cles of the heart. The two largest cavities of the heart, 
situated at its apex or point. 

Ver'te-bral Column (L. ver'tebra, a joint). The back-bone, con- 
sisting of twenty-four separate bones, called vertebrae, firmly jointed 
together ; also called the spinal column and spine. 

Ves'ti-bule. A portion of the internal ear, communicating with the 
semicircular canals and the cochlea ; so called from its fancied 
resemblance to' the vestibule or porch of a house. 

Vii/li (L. vil'lus, the nap of cloth). Minute thread-like projections 
found upon the internal surface of the small intestine, giving it a 
velvety appearance. 

Vit're-ous (L. vi'trum, glass). Having the appearance of glass ; 
applied to the humor occupying the largest part of the cavity of 
the eyeball. 

Viv-i-sec'tion (L. vi'vus, alive, and se'co, to cut). The practice of 
operating upon living animals, for the purpose of studying some 
physiological process. 

Vocal Cords. Two elastic bands or ridges situated in the larynx ; 
they are the essential parts of the organs of the voice. 



INDEX. 



A. 

PAGE 

Absorbent vessels 97 

Absorption 96 

by blood-vessels 96 

by the lacteals 96 

of the food 96 

Accommodation, function of 213 

Achilles, tendon of. 27 

Adam's apple 229 

Air. atmospheric 131 

Changes in, in respiration 132 

Carbonic acid in 138 

Composition of 131 

Dust in the 137 

Effects of impure 139 

Impurities in 136 

Matters in the expired ... 132 

Provision for purifying. 141 

Renovation by ventilation 142 

Air-cells of the lungs 125 

Air-passages 125 

Albinos 44 

Albumen 58 

of the blood 102 

Albuminoid substance. 57 

Varieties of 57 

Properties of. 57-58 

Albuminose 94 

Alcoholic liquors 77 

Physiological action of 78 

Alimentary canal. 81 

Animal functions 148 

Auimal heat 143 

how produced 143 

regulated by perspiration 145 

Animals, relative strength of 28 

Apoplexy 171 

Aqueous humor 210 

Arachnoid membrane 152 

Arbor vitse 154 

Arterial blood 107-135 

differs from venous 135 

Arteries 114 

Arrangement of 115 

Carotid 116 

Distribution of 115 

Pulsation of. 115 

Radial 116 

Temporal 116 

Arytenoid cartilage 229 

Asphyxia 250 

Assimilation 80, 121 

Audition 215 

13 



PAGE 

Auditory canal 218 

nerve 222 

Auricles of the heart 109 

15. 

Back-bone 21 

Bathing 47 

Importance of. 47 

Time and manner of 49 

Baths 48 

Different kinds of 48 

Belladonna 206 

dilates the pupil. 206 

Use as a cosmetic 206 

Bile 95 

Secretion of, in the liver 95 

Accumulation of, in the gall-bladder 95 

Uses of 95 

Biliary duct 95 

Bladder, Gall- 95 

Bleeding, how stopped 121 

Blind-spot 207 

Blood 101 

Arterial 107-135 

Change of color 107 

Circulation of. 107, 133 

Coagulation of 105 

Composition of 102 

corpuscles 102, 103 

fluid 105 

Microscopic appearance of 102 

Respiratory changes in 133 

Uses of the 105 

Venous : 107, 135 

Blood-vessels 114, 118 

Absorption by 96 

Injuries to the 121 

Body, renovation of the 66 

Bones 15 

Form and composition of 16 

Growth of. 22 

Microscopic structure of 17 

Repair of. 23 

Structure of 17 

Uses of 15 

Bowels 94 

Brain 150 

Anatomical structure of 152 

Function of the 172 

Injuries of the 173 

Membranes of the 152 

Reflex action of the 174 



t>(56 



PAGE 

Bread 72 

Bronchial tubes ]25 

Bronchitis 128 

C. 

Canals. Semicircular .223 

Capillary blood-vessels.. . . . 118 

Circulation in the 118 

Carbonic acid 132 

exhaled from the lungs 132 

:u the air 138 

retention in the blood 134 

Cartilage 20 

Arytenoid 229 

Cricoid 229 

Thyroid 229 

Casein 58 

Cataract 210 

Cells, Nerve 150, 159 

Ciliated 128 

Cerebellum 153 

Function of the . . . . . 172 

Cerebrospinal nervous system 150 

Cerebrum 152 

Function of the 172 

Cheese 58 

Chest, Framework of. 19 

Contents of the 19 

Chocolate 77 

Chorea 169 

Choroid coat of the eye 204 

Chyle 95 

Chyme 94 

Cilia 128 

Circulation 107 

in the frog's foot 119 

of the blood 107 

Rapidity of 120 

through the heart 112 

through the lungs 123 

Clothing 51 

Coagulation of milk 58 

of the blood 104 

Cochlea 223 

Coffee 75 

Effects of 75, 76 

Collar-bone 19 

Color-blindness 209 

Column, Spinal 21 

Combustion, Spontaneous 145 

Complexion 44 

Concha of the ear 217 

Conjunctiva 200 

Contraction of heart Ill 

of muscles 27 

Convulsions 169 

Cooking 70 

Cords, Vocal 126, 230 

Cornea 203 

Corpuscles, Blood 102 

Cosmetics 51 

Cranial ganglia 150 

Functions of 171 

Cranial nerves 154 

Cranium 19 

Cricoid cartilage 229 

Crystalline lens 209 

Uses of 210 



PAGE 

Cuticle 41 

Function of 183 

Cutis 42 



D. 

Decussation of motor and sensory 

fibres of spinal cord 164 

Dentition of infancy 82 

Diaphragm, Movements of the, in 

respiration 128, 129 

Diastole of the heart Ill 

Diet, Mixed 66, 85 

Necessity for changing 67 

Necessity of a regulated 62 

The best 63 

Digestion 80 

Circumstances affecting 97 

Gastric 93 

Intestinal 94 

Nature of 81 

Orgfins of 81-91 

Drowning: 250 

Duct. Biliary 95 

Nasal 201 

Pancreatic 95 

Thoracic 97 

Dura Mater 152 



E. 
Ear 

External 

Internal 

Middle 

Foreign bodies in 

Drum of the ! 

Bones of the ! 

Ear-sand I 

Ear-stones ! 

Ear-wax ! 

Eggs 

Composition of 

Emulsion of fats, in digestion 

Enamel of the teeth 

Epiglottis 126, ! 

Uses of 126, ! 

Eustachian tube ' 

Exercise 

Different modes of 

Effects of 

Importance of. 

Open-air 

Expiration 1 

Movements of. 1 

Extensor muscles 



Eve. 
Eyeball 
Eyelashes . . 
Eyelid3 — 



Fats 59 

Emulsion of 59 

Source of, in food 59 

Fenestra ovalis 224 

Fibres, Muscular 25 



INDEX. 



267 



PAGE 

Fibres, Nervous 149 

Fibrine in food 58 

of the blood 102 

Fish, as food 71 

Flexor muscles 26 

Food 53 

Animal 67 

Daily quantity of. 65 

Ingredients of. 54-62 

Necessity for 64 

Source of 53 

Vegetable 71 

G. 

Gall-bladder 95 

Ganglia, cranial. Functions of the. . 171 

Gases, Interchange of, in the lungs. 134 

Gastric digestion 93 

Gactric juice 91 

Action of. 93 

Daily quantity of. 92 

General sensibility 179 

Glands, Perspiratory 45 

Salivary 86 

Sebaceous 44 

Glos-ary 252 

Glosso-pharvmjeal nerve 189 

Gullet 90 

Gum 61 

as food 62 

Gustatorv nerve 189 

Gymnastics 33-38 

for schools and colleges 33 

II. 

Hair 42 

Uses of 44 

Hearing, Sense of 215 

Protection of 224 

Heart 107 

Cavities of the 109, 1!0 

Circulation through the 112 

Frequency of action 112 

Movements of the Ill 

Valves of the 112 

Heat, Animal 143 

Production of 143 

Regulation of 145 

Hemiplegia 165 

Humor. Aqueous 210 

Crystalline 209 

Vitreous 210 

Hunger 65 

Seat of the sensation of 65 

Hydra 149 

Hydrophobia 169 

Hygiene 13 

Hyperopia 212 

I. 

Incus 220 

Inorganic substances in food 54 

Insalivation S6, 88 

insensible perspiration 46 



Inspiration 

Intestinal juice 

Action of 

Intestines 

Complete digestion in the small.. 

Villi of the 



96 



Function of 205 

Iron. 56 

Proportion in the blood 57 

Proportion in the food 57 

J. 

Joints 19 

Varieties of 20 

Juice, gastric 91 

Intestinal 95 

Pancreatic 95 



Labyrinth 222 

Lachrvmal canals 201 

gland 201 

Lacteals 96 

x\bsorption by 96 

Lactic acid in gastric juice 92 

Lactometer 68 

Large intestines 94 

Laryngoscope 231 

Larynx 125, 228 

Production of the voice in the. 126, 228 

Lens, crystalline 209 

Ligaments 19 

Light, theory of 197 

.Lime in the bones 16 

in the food 56 

Importance of 56 

Liver 95 

Secretion of the 95 

Locked jaw 16!) 

Long-sight 212 

Lungs 123 

Capacity of 130 

Structure of 125 

Lymph 97 

Lymphatic vessels 97 

M. 

Magendie, on pain 181 

Magnesia, Compounds of, in food. . . 57 

Malleus 220 

Marrow of the bones 17 

Mastication 82 

Importance of 88, 89 

Meats 68 

The cooking of. 69 

The preservation of ti9 

Membrane of the tympanum 219 

Medulla oblongata 154 

Function of the 171 

Microscope 236 

The value of the 236 

Simple -2T, 

Compound 239 

The use of the 239 



268 



IKDEX. 



PAGE 

Milk 68 

Composition of 68 

Specific gravity of 68 

Milk-teeth 82 

Mucous membrane of air passages. 127 

Muscles 25 

Function of the 25 

Flexion and extension of 26 

Voluntary and involuntary 26 

M u.-cular contraction 27 

fibres 25 

sense 188 

Myopia 212 

N. 

Nails 42 

Uses of the 44 

Nasal cavities 192 

duct 201 

Nerve, Auditory 222 

Glossopharyngeal 189 

Gustatory. . . . . 189 

Olfactory 193 

Optic 197 

Sympathetic 158 

Nerve cells 150, 159 

Nerve fibres 149 

Nerves, Cranial ■. . . 154 

Spinal 156 

Functions of the ." . . 160 

Sensory, functions of the KiO 

Motor, functions of the 160 

Sympathetic system of 158 

Nervous system 148, 149 

Cerebro-spinal 150 

Nervous tissue, Properties of 159 

Nose 192 

Nutrition, Processes of 80 

O. 

Oesophagus 90 

Oil, Sources of, in food 59 

Old-sight 215 

Olfactory nerve 193 

Optic nerve 197 

Orbicular bone 220 

Orbit of the eye 199 

Organic substances as food 57 — 62 

Organs of circulation 107 

Digestion 81—91 

Respiration 123 

Sight : 198 

Voice -228 

Oxygen 131 

Amount of, consumed in respira- 
tion. 132 

Continually supplied to the atmo- 
sphere 141 

P. 

Pain, Relations of, to pleasure 1S1 

Sensation of 180 

Uses of 180 

Pancreatic juice 95 

Uses of 95 



PAGE 

Pancreatin 95 

Paraplegia 1(« 

Parlor gymnasium , 36 

Passages, Air 125 

Pelvis 19 

Pepsin 92 

Peristaltic action of the stomach... 92 

Peritoneum 94 

Perspiration, Daily amount of 4t5 

Sensible and insensible 46 

Uses of 46, 145 

Perspiratory glands 45 

Physical strength 29 

Culture 33 

Physiology 11 

Animal 11 

Comparative 11 

Human 11 

Vegetable 11 

Pia mater 152 

Plasma of the blood 102 

Pleura 124 

Pleurisy 128 

Pneumo gastric nerve 171 

Pneumonia 128 

Poisons and their antidotes 247 

Potash in the blood 57 

Potato 73 

Presbyopia 215 

Preservation of the teeth 85 

Ptyalin 88 

Pulsation of the heart 113 

of the arteries 116 

Pulse 115 

Form of the 116 

Writer 116 

Pylorus 90 

R. 

Radial artery 116 

Red corpuscles of the blood 102 

Reflex action of the spinal cord . . . 165 

Requisites for 167 

Uses of 167, 170 

Causing convulsions 169 

Objects of 170 

of the brain 174, 175 

Rennet 5S 

Respiration 123 

Change of blood in 123 — 133 

Frequency of 129 

Movements of 128 

Object of 123 

Organs of 123 

Respiratory labor 135 

Rest, necessity for 38 

Retina 206 

Retinal light 207 

Ribs, Movements of, in respiration. 128 

S. 

Saccharine substances 60 

Saliva 86 

Importance of. 88 

Secretion of 86 

Salivary glands 86, 87 



269 



PAGE 

Salt, Common 55 

Importance of 56 

Sclerotic coat of the eyeball 204 

Sebaceous glands 44 

Secretion of 45 

Semicircular canals 223 

Sensation of pain 180 

Relations of, to pleasure 1S1 

of temperature 187 

of weiirht 188 

Modification of 178 

Production of 177 

Variety of 17S 

Sense of hearing 215 

sight 196 

smell 192 

taste 189 

touch 184 

Sense, muscular 188 

thermal 1S7 

Senses, Special 177 

Sensibility, General 179 

Short-sight 212 

Sinews 27 

Sight, Sense of 196 

Organs of 198 

Skeleton 19 

Skin 41 

Structure of 41 

Skull 19 

Uses of the 19 

Sleep, Necessity for ,38 

Amount required , 39 

Small intestines 94 

Smell, Sense of 192 

Nerve of 193 

Uses of 194 

Soda in the food 57 

Sound, Production of 215 

Special senses 177 

Spectroscope 104 

Speech 227 

Relation of, to the sense of hear- 
ing 228 

Sphygmograph 116 

Spinal column 21 

Spinal cord 155 

Decussation of the 164 

Direction of fibres in 164 

Functions of the 162 

Nerves of 156 

Reflex action of 165 

Spontaneous combustion 145 

Stapes 220 

Starch 61 

Its change into sugar 61 

Diflerent kinds , 61 

Effect or boiling 61 

Microscopic appearance 61 

Stimulating substances 62 

Stomach 90, 92 

Digestion 9:i 

Movements of 92 

Secretion of 92 

St. Vitus' dance 169 

Sugar 60 

Varieties 60 

Sources of 61 



TAGE 

Sun-bath 50 

Sympathetic system of nerves 158 

Synovia 20 

Systole of the heart ill 

T. 

Taste, Association of . . 190 

Education of. 191 

Organ of 188 

Sense of 189 

Tea, Effect of 76 

Varieties of 76 

Tears 201 

Escape of the 201 

Teeth 82 

Temporary set of 82 

Permanent set of 83 

Bicuspid 83 

Canine 83 

Incisor 83 

Molar 84 

Arrangement of 85 

of different animals 85 

Preservation of 85 

Temperature of the body 146 

Extremes of 146 

Sensations of 187 

Tendon of Achilles 27 

Tendons 27 

Tetanus 169 

Thermal 50 

Thermae sense 187 

Thirst 65 

Thoracic duct 97 

Thorax 19 

Thyroid cartilage : 229 

Tissues, intimate structure of the. . 236 

Human 244 

of the lower animals 215 

Tongue 188 

Nerves of 189 

Sensibility 189 

Touch, Delicacy of 186 

Organs of 183 

Sense of 184 

Trachea 125 

Transfusion 106 

Trichina spiralis 71 

Trunk 19 

Tympanum of the ear 219 

Membrane of 219 

V. 

Valves of the heart 112 

of the veins 117 

Vapor. Animal, in breath 132 

Vegetable food 71 

Vegetative functions 148 

Veins 117 

Valves of 117 

Venous blood 135 

Changes of, in respiration 133 

Ventilation 142 

Ventricles of the larynx 229 

of the heart 110 

Ventriloquism 235 



270 



INDEX. 



PAGE 

Vertebrae 21 

Vestibule of the internal ear 223 

Villi of the intestines 96 

Absorption by 96 

Vital knot 171 

Vitreous humor 210 

Vocal cords 126, 230 

Observation of, with laryngo- 
scope 231 

Voice 227 

Organ of 228 

Production of 232 

Varieties of 233 



W. PAGE 

Water 74 

Action of, on lead 75 

Chemically pure 74 

Croton 74 

exhaled with the breath 132 

from springs aud wells 71 

Proportion of, in the blood 55 

" of, in the tissues and 

fluids of the body 54 

Pudgewood 74 

Walking, as a means of exercise. .. 31 

White corpuscles of the blood 104 

Wisdom teeth 84 



TSc 



6 37 



i 



